AST doesn't actually have higher APM than in ShB. It averages at about 42 CPM at high end gameplay and averaged around the same in ShB.

The problem with Endwalker AST isn't too many button presses, it's simply too many buttons, a lot of which are unnecessary fluff that doesn't add much. Not only is the toolkit bloated with fluff and filler, it's also very orientated at frantically pouring everything into your 2 minute burst, to the point that Lightspeed needs to be used just to facilitate this rather than being used for movement.

It's not smooth, flowing, rewarding gameplay. It's a jumbled mess that feels hectic to play. It's not even high APM, many dps and even DRK/GNB have similar or higher CPM. The fact that even DNC has similar CPM and still feels comfy to play just goes to show the real problem is AST gameplay.