Okay, first off, it's good that you were critiqued for your tech skill. Being technical and understanding the mechanics of the game is not a bad thing, and is in fact very desirable. Yet technical skill won't win you tournaments, not if your fundamentals and mastery of the basic elements of the game are lacking.
I'll give you an example from recent experience. I play PM competitively, but right now it's just low-level stuff. I don't have much technical knowledge or expertise (I can barely even wavedash), yet I've done reasonably well in bracket in any tournament I've been to. I don't have much difficulty beating opponents that are much more technically skilled than I am, because most of the ones that I've fought have been relatively sloppy in their basic gameplan and it's very easy to download their style and thereby punish their mistakes. They can be winning for most of the game because they can wavedash and chaingrab 'til the cows come home, but ultimately their plan is predictable and they don't mix it up enough to keep me guessing. It's not difficult to punish that kind of straightforward thinking, especially when you play Ganondorf, a character who thrives on beating down people who make fundamental mistakes. Even so, I get bodied when I fight players that have both good fundamentals and in-depth technical knowledge - and rightly so. They know how to play the game and they can exploit my relative inexperience, because they have better techniques than I do, and most importantly, because they understand the fundamentals of the game. PM is a game where tech skill is very important, probably just as important as fundamentals, but you need both if you're going to succeed.
Tech skill is good if applied well and it's a necessary part of progressing to higher levels of competitive play, but you won't get very far with just that; especially in Smash 4, where tech skill isn't as important as being able to play the game consistently and creatively. So if you're being criticised for being too predictable and not mixing up your gameplay enough - well, that's good feedback and it needs to be addressed!
If you're being punished for being predictable, it's because you're doing the same things in the same way and your opponent is able to read that and punish you before you even do it; even more than that, your opponent will deliberately bait you into responding in a certain way just to get the punish. The more you respond in a certain way, the more you reinforce the pattern both in your head and your opponent's head, and that makes it more difficult for you to mix things up and easier for your opponent to punish you for it. You might approach the same way every time, you might be throwing out unsafe moves, you might be playing aggressively when defensive play is better, or vice-versa. Sometimes it's not a good idea to try to combo at every opportunity; often the best thing to do is to play patiently and set up for a different kind of option, especially if your opponent expects you to combo. Whatever you're doing, you're not doing enough to keep your opponent guessing. That's a dangerous habit to have and you won't do very well until you can fix it.
If you want to be less predictable, the first thing you need to do is evaluate your playstyle and be perfectly candid with your performance. Examine replays of your games and ask yourself: what did I do here that I got punished for? Did I try to approach in the same way or use the same moves in the same contexts? Do I use the same movement options too often? Did I use unsafe moves when a safer move would have been better? You have to be able to recognise your own faults before you can work on fixing them. You probably don't know intuitively what you did wrong, because your mindset within a match is very different to your mindset outside of it, so it's good to review your performance from an objective stance, divorced from the pressure and immediacy of the match itself. Get somebody else to review it for you if you have to. Just make sure you know what you're doing wrong first: you can't fix something if you don't know what the problem is!
The next thing you want to do is practice varying your gameplan and fixing the problems you've identified. This can be very difficult if you've become habituated to perform in a certain way, so it's something you're going to have to consciously try to fix. Go to training mode and set up certain conditions, then respond in a way that you wouldn't normally, and keep doing it until it becomes muscle memory. Then do the same thing and find a different way to respond to it. Play with friends and force yourself to try new things until you don't feel compelled to do the same habitual things you've been doing up to this point. If you notice yourself falling back into the usual unsafe rut, force yourself to take notice and then try to do something else next time. It can help to play different characters when practicing, as this will help you get a feel for different playstyles and force you to hone your skills in different ways - for example, if you have difficulty approaching, it might be good to play a character with a wide variety of approach options, or if you can't play defensively, you can play a character that wants to stay back and be patient. Don't dismiss your main entirely, but try to branch out and experiment with new things. Diversity can help you refine your skills in ways you wouldn't be able to with just the one character!
Then you want to get better at reading your opponent. There's no right way to practice reading and no magic formula to make you better at predicting your opponent's moves, but the best way I've found to refine your reading skills is to take it slow and consider what options your opponent has in any given moment. Think about how they've done things themselves and whether they will do the same thing now. Know the optimal way to punish and be prepared to do something different if they mix it up. Never get complacent in your reads: if your opponent predicts that you will respond to their move in a certain way (in other words, if they read the read), they can react differently to throw you off or, again, bait and punish. Being able to read your opponent is just as important as making it difficult for your opponent to read you.
Finally, practice. Play with other, better people, go to tournaments more, just keep playing and never stop trying to get better. There's no easy way to fix your problems, but a good first step is identifying them and being willing to change. That's about as much as I can tell you. The rest you will have to practice for yourself - good luck!
