I’ve been conflicted about this. For example beehaw has a larger technology community but I’m a fan of lemmy.world so I try to post interesting content there to help the site.
Beehaw might not be the best example since it’s defederated but you get the idea
This is not the worst idea I have heard. I think it would be really cool if people could get local instances going for their cities. Then have the communities be based on topics relating to said city.