I've never seen anything like that. There's some graphical issues with clipping that at times make me wish the game had real collision physics, but on PS4 (where I usually play) character movement is quite smooth. What you're describing sounds more like a hardware glitch, perhaps combined with a lag issue. What platform are you playing on? If PC, are its specs up to the game's recommended specs?
Also, what control scheme do you use? While there are tradeoffs in either direction between whether to use a controller or keyboard and mouse, movement is one where controller seems to have a decided advantage. If you're currently a keyboard/mouse player, perhaps you could consider switching (though it would take a bit of getting used to).
It's a bit hard to tell here whether you're just over-simplifying your description or over-simplifying your gameplay. I'm not at endgame either, but as a level 50 SMN (not even a particularly good one) I already use a lot more skills than that. Counting pet actions and pet commands as well as your own job and role skills, you should have 43 combat skills by level 50. True, they're not all used in the midst of a typical fight, but there's a lot more than three that are. If you're simplifying your gameplay down to the minimum essentials, then that could be a major part of why you find it too simplistic and boring.
Nobody is saying that your opinion is invalid. What they're saying is that your opinion is an opinion, and talking about it as though it were objective fact is what's invalid. You personally prefer faster action. Not everybody does. So faster action might make the game better in your view, but worse to someone else. SE is trying to balance the game somewhere in the middle of a wide variety of player preferences. So long as you recognize that fact, it's perfectly valid to point out that your preference is towards the faster end of that spectrum, and to make a request for it.