It is as "easy" as that. My assumption is these are mostly optional things we think we "need" so a little friction finding something that doesn't suck isn't the worst thing. Reigns in our consumerism a little bit too.
For any smartphone I guess, can any one provider cut you off from using it? For Apple and Google Pixel phones that might be true, but not for all smartphones out there.
There are lots of custom Android running phones that you can truly own.