The fundamental problem with 4E was that it increased player burden/complexity. Because all the complicated thinking and decision making was moved to actual play rather than character creation.
You create a Pathfinder fighter and it’s a very complex process. But in actual play it’s “I move to closest enemy and hit with (preferred attack method inserted here)” Sure you have complex characters like Wizards where you choose and deploy spells and keep track of a dozen resources… but that’s optional.
D&D 4e turned every class into a wizard. You all had the same level of tactical complexity (at wills/encounters/dailies), and tactical movement on the mini-map became much more important to everyone (in D&D 3/Pathfinder only the Rogue cared about movement). This increased player burden, and thus people complained. Note the big complaint was that it played like a video game, where complexity is something that occurs in actual play because all the front-loaded stuff is done by someone else.