You’re right, but there’s more to appreciate about needing to choose an instance.
It’s like email. All email services work with all others, but the end user still needs to choose a good one. There are more than one "good one"s, and part of the decision is about personal taste.
And sometimes you have to leave a bad provider for a better one. Look at my account, it’s brand new. Because lemm.ee has had one too many federation issues for my taste.