Basic rule if someone claims X magically solves a problem they don’t follow X and are a huge generator of the problem.
For example people who claim they don’t need to write comments because they write self documenting code are the people that use variable names x1,x2,y, etc…
Similarly anyone you meet claiming Test Driven Development means they have better tests will write code with appalling code coverage and epically bad tests.
If you signup to social media it will pester you for your email contacts, location and hobbies/interests.
Building a signup wizard to use that information to select a instance would seemto be the best approach.
The contacts would let you know what instance most of your friends are located (e.g. look up email addresses).
Topic specific instance, can provide a hobby/interests selection section.
Lastly the location would let you choose a country specific general instance.
It would help push decentralisation but instead of providing choice your asking questions the user is used to being asked.