You showed good fundamentals such as good spacing, stutter stepped smashes, pivot grabs, angled forward smashes.
You need to space f-tilt more. I noticed how you would choose to go in at Marth's shield with a fair and it usually left you getting punished. If you're going to go in on someone's shield, at least from the air, you best either be sure that you can outspace their punish or be a bit mindgamey about it as in maybe air dodging behind them into a downsmash.
Here's a tip when recovering high, especially if you are struggling with b-reversals. Turn your back towards the stage when you recover and be flying towards the stage. When your opponent begins to chase your direction, immediately spam back airs while fast falling. This will generally put you in a good position to recover.
10:20 - You have the right mindset at trying to get under Marth when he fair's your shield, especially when it's poorly spaced. Well executed @ 18:36 though.
10:22 - Dash attack --> U-tilt. Very nice. After a low % u-tilt, you can still shadow his landing and punish it. Try to get into that mindset. Also, if they DI away from your initial dash attack, then you can usually charge a forward smash and let it eat through their air dodge. If they DI too far away tho, you may just have to settle with a d-tilt or if you're quick enough, perhaps another dash attack.
10:30 - 10:40+ - Try your best not to let Marth pressure you to the side of the stage. It's very easy for him to do and it just puts you on the ropes. Marth is good at that. So if you get one good GTFO move in, then follow up some if only just to get more stage control.
11:24~ - Altho you have the stock advantage, it's really hard to camp Marth imo. So, to me, you shouldn't be afraid of going inside of him and trying to fight him. I saw a lot of dodge rolls around this time, and let me tell you, he has one of the worst rolls in the game. You were just asking to be killed at that point. If you really feel the need to get away, perhaps a short hop airdodge away might work, or just simply run haha.
11:36: I know that spot dodge -> downsmash probably feels very nice and fluid to use, but don't execute the downsmash unless you know it's going to hit or you're just asking for it. Spotdodge to grab in this case would have been better. ROB doesn't have a load of options so you must consider them wisely.
11:46 - When recovering, either high or low works against Marth, going right for him isn't really a good idea especially at kill %. If you recover low, go to the ledge and work from there. If you recover high, work with b-reversals, backairs and such to juke a landing.
12:44 +12:46 + 12:50 +12:57 - You need to try and mix up your landings a bit instead of airdodging into the ground. Whether it's spacing a landing with bair or what have you, try something different. If you are going to airdodge into the ground, at least make sure it's fast fallen or timed well.
13:10 - At this point, you need to edgeguard the piss out of him. I would have done it with a b-reversed up+b and then if I grabbed the ledge too soon, timed a back air off the ledge which can easily beat Marth's up+b.
15:23 - NEVER and I mean NEVER blow your second jump like that. I know it's common knowledge and you may not think you'd need it with ROB, but trust me you do.
15:25 - Too risky, just fly under the stage. Or, if you had your second jump, you could of jump+air dodged back to the stage. I know you made it back okay, but generally...you shouldn't have.
16:00 - If you watch closely, Anaky uses his second jump. Knowing that, punishing his landing is more crucial than ever since one, it can kill him easier, and two, it should be easier to know where he's going and what options he has.
17:05 - Go to the ledge man. Force him into fewer options. If he up+b's onto the stage, then punish it. If he tries to space an up+b onto the ledge, then back air him for it.
17:17 - Good grab. You can do that to dancing blade every time if he goes too many hits in on your shield. Keep that in mind.
18:50 - The nair here was actually fine if you had boosted it with up+b. If you had, as I'm sure you're aware that ROB can rise if he does a move out of his up+b by simply pressing up after the move is done [you showed me you can do it at 19:58, so try doing it to mindgame your opponent], he would have whiffed his upsmash and you could have came down with a nair, bair or what have you.
20:00 Grab before the last swing comes out. Always works.
Your first stock - You lost so much % due to not mixing up your recovery. This is a good example as why it's always useful to have different approaches to everything and why I think b-reversals would help as well.
Good job maintaining your composure that stock tho.
21:32 - Stop running straight for the edge lol Such a bad position to be in. I used to do it a lot too so I know where you're coming from. Marth just kind of naturally puts us there, but don't help him more than you have to
Your second stock - You seemed to play pretty scared this stock and I think Anaky sensed that. A lot of % here was just lost on fundamental things such as attacking shield when you could have grabbed, airdodging too the ground, and poor recovery choices.
22:40 - Anaky has seen you airdodge into the ground so many times that he's starting to think ahead on it, good idea to switch it up here with a jump. Also, rising up+b's, as mentioned before, are really nice for this as well.
Your third stock - You seemed a little desperate for % here. It's hard not to be when victory is slowly slipping out of your fingers. If you got an attack, you kept trying to follow it up with another one I felt and ROB can't particularly do that. Especially not in the air. You have to be patient and get those reads after you hit them. Maybe appear to be aggressive and then back off. Try provoking airdodges. Make them play your game.
The Wrap Up
That's about it. I hoped you enjoyed this thorough critique and I definitely hope you benefit from it. Your ROB shows a lot of potential in my opinion. You know how to be aggressive and you know how to play campy. The most troublesome thing to decide is when to do which. You pick that up the more you play. Not saying that what I suggest is particularly right, but this critique is how I would have tried to approach your given situations. If you have any questions, don't hesitate to ask.
I'm going to be doing though at low % is it possible for opponents to get underneath with good DI?
Even if so, it has never happened to me so it probably isn't practical that it will happen. I would personally say no though.
Only fair Marth if he fairs your shield, that's the only true way ROB can beat it out.
Fair him when you see fit, just not when he's grounded and shielding. It's still too good of a move to ignore. Even in this MU.