Why doesn't pve have pvp combo structure?

[Seraphor]

I don't think muscle memory is that different between 1-2-3 and 1-1-1. As such I don't see why it wouldn't be able to work with DRG.
MNK would indeed require the most work to adept, because it's the most mechanically ingrained with the current system. On the flip side, MNK has been a mess for many years now and hasn't seen it's gameplay evolve since ARR, so maybe taking some more liberties here and re-imagining the whole job might be an option too.

Either way, I'm only suggesting consolidation isn't bad when used to evolve the game. Because most people opposing it in here seem to think consolidation will result in simplification, which isn't necessarily true. Yet cry out every expansion when half their skill bar gets deleted, which is a direct result of NOT consolidating.

On the contrary, I've just explained why consolidation of those melee jobs actually makes them more complicated.
With individual steps of the combo having unique effects, you need to keep track of where you are in the combo, and as I explained with MCH's Heast Blast 'combo', essentially a 1-1-1-1-1-2 combo with weaving, you need to make sure you're counting your GCDs. If you don't, you miss that last '2', dealing 1/6th less damage with Wildfire and clipping your GCD which knocks your damage output down, potentially unsyncing your rotation if you keep doing it.

In other cases, muscle memory can do this for you, instead of counting 1-2-3, you're pressing X, Circle, Triangle, X, Circle Triangle... or whatever keys you've set them to. You know when you get to the last button in your sequence, you move your finger/thumb back to the start.
With the combo all on one button, you need to count, constantly, in order to ensure that the specific skills in the combo line up properly.

The reason this isn't an issue in PVP, is because PVP skills have been simplified to remove all of this nuance, so that you can focus on the battlefield, and react on the fly to your opponents and teammates actions, instead of executing a rote-learned and fixed rotation.