the alternatives only supported very few phones.
I only purchase phones I know I can install alternative OSes on. When one of my current ones is getting too old and in need of replacement, I research what the current alternative Android OSes are, chose a bunch I find are nice enough, then find the list of devices supported, the chose one from among those that's within my budget range. Those tend to be Motorola, whether officially or via some hack.
I don't buy a phone to play games, which means most any phone is performant enough for my needs, so I go with the cheapest option that does what I actually need. This also means that warranty is irrelevant: if the phone breaks for some weird reason, which is rate, getting it serviced by paying for the service, or buying a new one outright, aren't a big deal. Hence, the moment the new phone arrives I follow the procedure to get it unlocked, then the new ROM into. Sometimes with Google apps, sometimes without, depending on what I'm using it for.
As for bank apps and the like, I keep an old, tiny, cheap phone with stock, years-old Android that banks, due to mysteries of the universe, consider "secure" despite having hundreds of unpatched holes all the way down to the kernel. When I need to do banking I pick it from the docs drawer, turn it on, do what I need, turn it off, and back into the drawer it goes. For everyday use I have a debit/credit card, no app necessary with them.
Streaming is a loss, but eh, YouTube works well enough either with the official app, an alternative one, or a mobile browser, so good enough for watching something on the go. For me that suffices.
But yes, for those for whose use case is way more mainstream that's certainly not a good fit.