It think you'll find there's an enormous amount of disagreement over most of those things you list as problematic or clunky. They may not be perfect but they are the product of years of experience, development, and evolution of the rules. And, in my experience, they work surprisingly well compared to other editions and even games. As much as I like aspects of PF2's 3 action economy and its simplicity, there are definite issues with it that I do not like such as restrictions on actions that can't be performed first in a turn, raising shields every round being necessary, and the tendency of anybody to make multiple attacks even if the chances are low just because they have the actions left and don't want to waste them.
I briefly tried PF2 and saw all the things you describe here. The 3-action economy is great in principle, but actually felt like a straight jacket to me because of all the provisos, and especially because, with that supposedly general economy, you still had to be able to complete anything you do* on a single turn. If I had the option of casting a 3-action spell, for example, using my last action on my turn, and then finishing it with 2 actions on my next turn, combat would be
much more interesting, firstly because that would be an option
at all, but also because I'd be risking interruption of the spell, enemies would be motivated to interrupt it (possibly distracting them from doing something worse), and my teammates would have to cover my butt in those moments (or choose not to, of course, depending on what was tactically most important).
* I'd originally written "any action", but then the word "action" is unfortunately reserved for the currency of, erm, actions.
But, this thread is about 5e, so I'll say that an action economy based on distinct categories of actions is definitely annoying, what with some abilities using your action, and others using your bonus action. So, if you have two abilities that use your bonus action, nope, you can't use them both on your turn. Even a minor change like saying you can sub a bonus action for your action (that is, you can do an action and a bonus action, or two bonus actions, but not two actions) would be an improvement—albeit a band-aid on an underlying kludgy action economy. Another band-aid might be class features (or feats, or magic items, or what have you) that grant an extra bonus action or reaction on a turn, the way some classes get an extra attack (maybe with limited uses per short/long rest, maybe not). That's getting out of describing the problems and into the messy area of changing a large, complex system, though (as billd91 alluded to), so I won't take that any further.