My "is it worth even thinking about a particular device" litmus test is "can it run CM". Unfortunately that's impossible to tell for future devices, most of the time.
LG's older LG G4 still only runs CM on two variants. The international one (H815), and the T-mobile (H811) models as these are the only ones easily unlockable bootloaders.
Totally agreed. Also it's hard to tell for current devices as reviewers, such as Engadget, Ars or GSMArena, never mention it. It's surprising given that tech review sites target many power users.