The features I’m asking about here are available for the other competing engines like Unity and Cryengine. I’m not sure why Unreal would want to shoot for having fewer features or be less complete for advanced development than the others.
The main concern here is that a separate animation system from behavior create more problems and more work for everyone than it save; for the reasons already explained. Menus and effects are orthogonal to behavior and are not of concern here. A menu is not trying to change the movement of the character. An effect does not try to change the animation of the character. Those are non-competing systems. Animations are intertwined with behavior. The behavior of throwing a punch and the animation of throwing a punch work together. These are two systems are competing over the character - logic pulling at the character one way, and animation another, the way UE4 does it.
After a while in development you stop worrying about what looks nice and worry more about what gets the job done the quickest with the fewest problems. You start realizing you spend 10% of your time coding and 90% of your time debugging. The animation system in UE4 tries to save you time in the 10% - exactly the wrong place to put your efforts - and adding to the debugging time. After a while you also realize that it’s more important to have flexibility in your system than a slick interface. You can’t go to a designer and say “we can’t do that feature because it doesn’t play well with UE4”. At the end we’re in the Entertainment industry, and producing creative, fun, original content is more important than anything else. I’ll take working harder and developing a more impactful game over doing an easy job that produces mediocre products. In my particular case, I believe doing it my way be both easier and make more impactful products in the long run, and that’s what really matters.