> If Samsung or Xiaomi or Google could sell you a better phone with a replaceable battery, they would.

I do not think they are colluding, but they are definitely chasing the same trends and users preferences don't seem to play that much role, unless it is one of the few essentials things. Effectively, users do not have much choice except in few areas. All phones being the same is not just because "everyone likes their phones to be unpractically huge or slow" .