I agree 100% with you. I am in a similar situation, rooted and unlocked, slowly but surely getting access restricted.
Google is trying something which will be a net negative for everybody, instead of keeping this _massive_ USP that also keeps a core userbase. Might as well switch to iOS now, I don't have anything which keeps me on Android.
They've been chipping away at this over the years. Safetynet was the first offense, but if they start restricting app installation from sources of my choice (I hate the term "sideloading"), there's not much advantage left.