If the average user can't handle flashing a custom ROM (which is probably true), they can take it to one of the million phone repair shops and give them $10.
It's not just a question of flashing it, it's a question of living with it. By all accounts I've read the custom ROM experience is far from seamless: it sounds worse than the Linux desktop currently is, and I wouldn't recommend running Linux to just anyone.
It's really not uncommon to see ROMs with known bugs like "camera doesn't work" "3.5mm port doesn't work". When I was looking for a phone in 2018 I was looking at the Pixel series and that was the bug list for most of the ROMs at the time - and pixel was basically the best-case scenario that everyone was pointing me at as far as support.
It was still in official support at that time but I got burned by my first android phone going EOL within 6 months of when I bought it and I wasn't going to leap again without knowing there were actually ROMs that worked without major feature loss.
It probably would have worked out, being a pixel and all, but I specifically ran into bumps on my previous phone (Moto G Falcon) with features being lost on custom ROMs. Eventually I found one that worked OK but that's just not acceptable to lose official support 6 months after purchase and deal with custom ROMs where random shit is broken.
That's right, and that's why you should choose your phone based on the ROM you want. Of course if you choose a phone that is not supported, it probably won't work well.
Try running the Samsung S23 ROM on a Nokia 7 plus and tell me how it goes: that's the same problem.
I have been using /e/ OS on a Fairphone for 2 years, and it is absolutely great. I just use it like a normal Android, no need to fiddle with it _at all_. Some apps don't work because I'm de-Googled (no Play Services), but you don't need that (or you can accept that some apps don't work).
This wasn’t my experience with de-googled (edit) grapheneos.
One week, apps started throwing an uncaught null pointer exception on startup because their network permission was revoked.
Even without that, random apps (especially for charging EVs and parking, and especially if it was raining) would just plain break for a few weeks, then start working again.
It would be nice if there was a commonly-used android compatibility suite for developers (of apps and of roms), but there isn’t, so everything is flaky once you are slightly off the beaten path.
That wasn't my experience with GrapheneOS: it's been rock-solid (and the battery savings from not having apps constantly polling for updates means I get 2.5 days per charge on both my Pixel 4a and Pixel 6a.
They work excellent for what they are, and are a testament to the ingenuity of the android community, but as an end user product they're just not there yet. I would never flash a custom ROM for someone who isn't capable of flashing something else on it to fix a bug or restore back to factory.
Phone makers make it hard, but it doesn't really have to be. You can flash GrapheneOS on a Pixel using a USB cable, Chrome and a few pokes at the developer settings menu on the phone. The only actual friction comes from the Pixel's default OS and that UX flow was a choice.