I'm gonna say you won't be able to be
really good at this game without the ability to do advanced techniques. You won't be able to win tournaments. If you want to just be good enough to beat most people (online, or with random people offline), it's possible, but you'll probably need to pick your character with that in mind. Heavily combo-oriented characters will probably be a bad choice.
With all of this being said I don't think your issue is necessarily timing, but rather you aren't trying to get into your opponents head to figure them out enough. A player could be perfect when it comes to execution but if they're predictable then they're not going to be beating many other competitive players.
Right. On For Glory in Smash 4, you can encounter plenty of Bayonetta or Ness or Captain Falcon players who can execute some combos once they get it started, but who are bad at other aspects of the game. They have the timing down for some techniques or strings but they are too predictable and not good at adapting or reading, etc. Figure out how to stop them from getting their combos started or how to break out of it and they don't know what to do.
I'm not great at combo strings and can't do all the advanced techs, but I've beaten plenty of people online who are better than me at those aspects.
But I'm not about to be winning any major tournaments either because truly high-level players will have both the technique and the mindgames and such.
Another thing is that if you want to get good at those aspects, you will need to practice them. I don't put that time in because I'm not that serious. If you haven't actually put any time in practicing that stuff to get the timing down, you might not be as bad as you think - you just don't realize how much practice some of those better people are putting in. It's not all stuff most people can just get without practice.
But yeah you can't be a high-level tournament player without that stuff. You can definitely get to "Elite Smash" on Quickplay without it, however. So it just depends on what you mean by "good".