Google is literally the only manufacturer that lets you unlock your phone day 1, officially, without any "e-fuses" or warranty voiding, with step by step instructions on their own website, and you're saying they are killing custom ROMs?
Perhaps custom ROMs are dying because people don't feel a need to flash them? I haven't flashed a custom ROM in probably 8ish years, because my phones stock ROM has everything I want. I no longer need to flash a ROM for flashlight toggle, screen recording, scrolling screenshots, etc. It's all built into my OEM ROM.
I hate Android updates mostly as Google seems to want to restrict it down to Ios levels recently.
They seem determined to make it hard to use emulators and to kill off apps like tasker.. My latest experience has also been soured by having a nothing phone were every update seems to introduce more issues and not even attempting any bug fixing or optimisation it's turned what was a pretty good phone originally into a constantly rebooting pos.
I went Graphene a while ago and I couldn't be happier. I understand that's not a solution for everyone though. Especially since some banks require SafetyNet. And GPay (which I don't use) doesn't work.
Still, I would definitely recommend considering it.