You’re welcome to go to a different instance. That’s the entire point of lemmy. If you don’t like how an instance is ran you can go somewhere else.
I don’t think what you’re describing is technically feasible. If it worked how you describe, then when someone makes a community that instance would have to somehow go and ask every single other instance in existence - hey do you have this community name already? We wouldn’t be able to like, keep a database of all the existing communities everywhere.
It’s kind of the entire point of lemmy, it’s decentralized. Nobody can control other instances. There’s nobody “allowing” it including the lemmy devs
these are different communities with the same post in them
These menus are have been completely overhauled to be iOS 14 style, so this will be fixed