What about people who kinda gave up tinkering with custom ROMs because the state of the stuff that matters (root checks by your mandatory banking app, some Google stuff) is either not documented (good luck finding an overlap of "phone model" + "your local bank app" + custom ROM" as a tested and known-good thing).
I'm all for freedom and choice, but I don't think unless you're willing to go through a couple of phones, a couple of days of work, or are a specialist in the first place, this is a reasonable way of action for average phone users. I know you said "power users", but I'm a power user with computers, my phones could be a lot dumber if I had my way - but it won't happen if we have to increasingly use them as MFA devices or be at the whim of corporations with a better lever (i.e. banks, I'm not changing my bank account 3 times until I find one with an app that works on a rooted phone...)