Alright, I'll give you what advice I can. But for future reference. Even playing vs a casual friend is better than posting a vid vs a cpu.
Obviously I can't judge your reading ability or mixup game vs a cpu. But here's the stuff I noticed.
First thing, pretty easy to fix. When you are uairing the opponent on the platform, you are jumping up past the platform and exposing yourself. Shorthop and do the aerial so that you don't leave yourself as susceptible to a followup attack. This is very important. Otherwise people can just spotdodge your aerial and punish you with dsmash or something. If they know they can do this, they no longer
fear the platforms, and you are screwed. You need them to be
afraid to stand on them. Uair correctly. Also, use nairs at low percents to go for the sheild push-> dash grab out of the air or IB reset->grab. (on the characters it works on)
Learn to buffer your throws, you were going very slowly, and a half decent masher would render your cg virtually useless at that speed and they wont be
afraid of it.
Along the same lines, you kept sliding, which is ok occasionally, and is better than dropping the grab. But when it happens THAT often it means that you really need to work on what I'm going to call finger discipline. Being able to move your thumb (or whatever other fingers you may use for the analog stick if you're some freak like Hylian) consistently and confidently the correct distance in the correct time frame. It looks like your finger is probably holding the direction of the throw too long or you're moving it from one side to the other too quick/slowly or something. And the fact that it happens maybe half the time means your finger motion is not consistent. Once you train your finger to do the same thing every time you will see an extreme reduction in those sliding moments.
Work on your spacing. You kept leaving yourself open within squirtle's attack range and got punished for it repeatedly. you want to continually remain just outside of it until you see your chance to punish endlag for an attack/make a read on what they will do next/etc, or dash in then out to bait something.
Know what options your opponent has, and how to beat them. (has to do with previous point) You can pivotgrab squirtle out of literally ANYTHING he can approach with. Remember this. For other characters you will be need to wait for the powersheild punish on certain moves. If you learn what you can do in response to each move before the match even starts, then you will have a clearly defined flow chart you can use in response to their patterns of attacks/approaches. vs squirtle, I literally just sit there desynched IBing (to force an approach)/blizzarding until he approaches. Then on their first approach in range, you go for the pivograb. If you get them with it, excellent. Kill them. Now they will be required to approach even more, yet they'll be significantly more
afraid to do so. You want this. It is how we win.
That is another reason to make your cgs more consistent/fast. I've had many people tell me they often try a stupid aggro approach early on vs an ICs they haven't played before to see if they need to worry about their cging abilities. If you drop it, or do it at a speed which allows them to mash, then you're already done. They wont be afraid and will tear you to shreds. The stock you get from the cg isn't why you need it. It's the fear that your opponent's knowledge of it causes.
Fear hurts more than chaingrabs.
Now, say they get out of range in time and you don't get the grab, or you land a pivotgrab and now they know. The next time you THINK you can get the pivotgrab on the player from their approach, just sheild and see what they do. If they airdodge away or stay out of range instead of pushing in with their aerial or whatever, odds are they are trying to bait you into the pivotgrab so they can punish. This is what smart players will do. You can respond in one of 2 ways.
One is by running after them and calling their approach bluff with aerial punishes or grabbing them in retreat if you're able. The other is to just let them attempt to bait a few times. Then you play the guessing game. They are going to have to put themselves at risk and go for a hit eventually. If you aren't biting on the bait that means they are going to have to risk actually going in to harms way occasionally to hit you. This is great for us. It essentially puts us in a situation where you either guess right, and get their stock. Or guess wrong and lose ~15-25%. This means they have to win the reading game at somewhere around a 4 or 5 to 1 ratio just to stay even with you. I'll take those odds any day.
But again, this is assuming you can get the kill off of the grab.
Practice, practice, practice. I started playing ICs as a secondary as well. However this was after I had been maining pika for over a year, so I no longer needed to practice my main's tech skill much, it was all second nature. I practiced with my "secondary" ICs ~10x as often as I practiced with pika. This is what is required if you want to get decent with this extremely technical character. A lot of times people start with them as a secondary, but because of all the time they put in and the improvement they see as a result, switch to maining them.
If you don't practice, then nobody decent will end up being afraid of your ICs and you've already lost with them before the countdown to the game starts on the screen.
Everything I said about Squirtle can be applied to a lot of other characters btw. Wario being one of them.
Here is a match which I think demonstrates a lot of what I'm saying. Notice how on the beginning the Wario is staying on the platform. I respond by
safely uairing him through it without exposing myself like I mentioned earlier. Using this strategy
correctly, I can essentially just keep dealing damage to him slowly but steadily with virtually no risk of taking damage back at all. Notice how I'm going for the uairs only when he's landing, or poking up just as he jumps. These are the times which he is least likely to be able to punish the poking. A landing opponent is a vulnerable opponent. Learning how to punish landings with ICs both on platforms and on the main stage is absolutely essential. Make them afraid to land, and they'll do stupid, habitual, and in turn predictable things out of fear.
It doesn't take long for the Wario to see that he can't win while just jumping around on the platform. All that's happening is he's taking damage and not able to deal any back through my safe poking. Now he has to come down from the platform to try to get a lead on me somehow. You see me go for a few pivotgrabs as he attempts to find a way in. He stays out of range, but he eventually makes a mistake and mis-spaces a landing.
Everyone screws up eventually. All you have to do is keep playing safe and wait. I get the grab and kill him.
On his next stock you see him attempting to come down and getting punished a few times. Then I **** up a pivot grab input and put myself at the edge of the stage. Which takes away my pivotgrab option. The wario sees this chance and moves in. I make a mistake and drop my shield which allows him to separate me. He doesn't capitalize as much as he could have, but like I said, if he gets in then you lose maybe 30ish percent. If I get in, it should be way more. The reads:stock ratio favors me heavily. So I don't sweat the minor setback. Once I get nana back I run to a safe position and begin establishing stage control with Ice blocks. I see him use a grounded get up option and go for the Ice block chaser grab. At this point I **** up the grab after a few reps (cging wario on YI is not my forte
). Notice how he immediately starts playing more aggressive and less afraid. Luckily he ****s up and lands poorly before he got too much momentum. But if he had been playing smarter aggro there he could have done a lot more damage. After I kill him with that cg he starts trying aerial approaches over and over. He hits with one or two. But I know that pivotgrab will beat every one of his aerials. So I dash back and look for him to come after me with another aerial (he hit with the last one, stands to reason he would try again). free grab because I knew how to beat all his aerial options.
I try to end early since as you can see, I was not confident in my cging on wario with that curvy floor. I was
afraid of dropping it if I tried more reps, so I ended with a smash. He lives. After that I pretty much know the game is over and start going all in until I get the kill.
So main things to work on.
Punish platform camping more effectively, using aerials at the right times, and at the right heights so as not to get punished for your pokes. Harder to land the grab on platforms so
scaring them off of them is important.
Practice the chaingrabs. Get them faster and more consistent. Make your cging good enough that people actually
fear it.
Learn what beats each move/approach that the characters you intend to use ICs against have. (Wolf's back air, Marth's fair, Metaknight's tornado, Wario's dair, etc)
I also didn't really see you using desynchs. If you can't, learn how. Even just one or 2 simple desynchs will suffice. I usually stick to just the dash dance or pivot desynchs, which are both easy enough to learn. If you know how, learn to integrate them more seemlessly into your play and WHEN to integrate them into your play (aka don't try to blizzard wall a diddy with a banana in hand).
And remember. An
afraid opponent is way easier to beat than a confident one.