I understand what you're asking for - but really you may be better off with an iPod Classic and amp. The GUI is what it is.
FWIW - I agree with some of what you are saying - my biggest gripe is (in category/tagged browsing) not having everything sorted into Artist/Album/Track - eg when doing All Songs. But that has been like that since first introduction.
I'd imagine the X7 with it's Android interface will solve a lot of the GUI "issues" (at a higher cost of course) - but IMHO any expectations of the X5 (or even X5ii) GUI being as good as the well polished Apple GUI is (like you said) "irrational". If you're coming from Apple ecosystem - you're going to get frustrated. If you're coming from something like HiSound Audio or other boutique DAPs (non main stream) - you're going to love the Fiio. Different perspectives.
What you get with Fiio is great sound, and (again just my opinion) extremely good feature to cost ratio. Expecting more is going to lead to frustration long run.
Not sure if they can implement the fast start they have in the X3ii with the X5 hardware (maybe the next version X5ii) - but one option is to simply turn off "Idle Poweroff" in settings. As long as you remember to manually turn it off when you need to, it will work. If you forget though, you'll end up with a few flat batteries ...... "trade-offs"