There isn't user choice, only developer choice. For example, if I want to play Fortnite with my IRL friends I must download Epic Launcher. If I want to play WoW with my friends I must download BattleNet, if I want to play Counter Strike I must download Steam. I don't get much choice in what my already existing community of friends decides to play. This is likely to be mirrored in phone app stores. Need whatsapp/facebook/instagram on your phone? download the Meta Store! Don't like their T&C? Pound sand.
Don't like their T&C, don't use them. As simple as that. I do not like Trucaller's T&C, so I do not use it. If some day I don't like WhatsApp's T&C, I won't use it. My friends and family will be asked to contact me via Signal (as an example).
To your examples with games, there are lots of games that I do not install simply because I don't like those launchers. Whats wrong with that? It is _my choice_. I am not forced to use only Windows Store, for example.
The argument that "because third party app stores can be shitty, they shouldn't be possible" is strange.
