There is for sure a lot of stuff they could do to reduce necessary buttons while not really changing the way the game plays.
A lot of it could even be a toggles type of thing like having a separate page in the skill book. Like an Dynamic skills buttons tab
The thing that is weird to me is they actually already do a lot of it seemingly randomly
Can just use warrior as an example even though it really is among the least problematic classes already just because I'm most familiar with it and use the 90 set just because
Right now we already have fell cleave/inner chaos and decimate/chaotic cyclone as dynamic buttons but oddly enough having a forced regular fell cleave on a sidebar would actually be preferable because their are times inner rage and inner release decide they want to line up and inner chaos during inner release is pretty wasteful. So can add a button there because who cares about the aoe efficiency...
raw intuition and nascent flash are being made into basically the same skill in targetable and self versions. Could easily just make it one skill with passives that upgrade it into targetable and bloodwhetting stages. Trim one button there
Could easily make a storm's path dynamic button and storm's eye still branches at the same point. 1-1-1 and 1-1-2 is not really any less skill than 1-2-3 and 1-2-4 The skill is in weaving and knowing when to use which finishing skill not ability to slowly roll a finger across buttons. Can easily trim 2 buttons there
The new 90 skill only is available after inner release is used and has a shorter active duration than inner release's cooldown. Could have a dynamic button for that to trim one button needed.
So you could pretty easily make a targeting macro to nascent flash tanking partner and add a straight fell cleave button to your bar and not still be at the same button count at 90 compared to 80
It's pre-existing ingame tech so wouldn't even be difficult in the least and warrior is already fairly well optimized so other jobs could Trim a lot more.
The second thing is every cooldown ability does not need a matching aoe variant. Just add a splash damage passive to them if it's such a big deal to have an aoe rotation that is a 1:1 match with single target.
The last is some classes have skills that seem to be absolutely nothing but filler. Like sonic break and bow shock on gunbreaker; you could remove those skills and put a little potency somewhere else and the class would basically be unchanged. They're not tied to any mechanic or resource or anything, was like "here's a complete functional class and 2 extra skills on the side". I'm sure that exists in other jobs too
Just to me personally feels like you could reduce button bloat quite a bit and make it a player choice and cut out a bunch of redundancies that don't really add anything to the classes and in the cases of stuff that is already automated give the players a choice to make it manual too