Custom ROMs nowadays require you to be scouring Qualcomm out of tree source repositories (or firmware dumps of equivalent phones, I think, in the case of Mediatek). It's impossible to guarantee quality with this conditions. Even if you just want to have a pristine kernel tree of the original firmware you may find, if it was ever released, it was squashed on the wrong source commit (again, laurel_sprout, though a random Github angel fixed it).

So Google's devices tend, thankfully, to have better sources. Additionally, GOS team is competent and, for now, sustained full-time by donations. Those three conditions are what allow GOS to be a very good ROM.

Do note: it has its quirks, specially with the new trimestral code dumps by Google where half-baked features are on the source (though disabled by feature flags).

I used to do home banking from my bank's website. Recently, they created a digital-only branch for customers who mostly do home banking and only rarely need to go in person to the bank. They asked their customers if they wanted to switch and offered services at the same or lower cost than before. I made the switch, but found out that unfortunately the new website lacks some functionalities that are only available from the mobile app. I guess they are assuming that most people would just use their phone anyway and didn't bother to reach feature parity between the website and the app, preferring the app.