> your existing users have a very different set of needs and priorities as new users coming onto your platform, or not yet users you want to attract

In this case you should side with your existing users who 1) you already convinced to sign up and engage with your product 2) helped you build your product in the first place.

I’d take an established power-user any day over a potential new user that has yet to prove themselves (they might quit the platform as quickly as they joined).

Of course, some idiots don’t understand this, and “Twitter” is the result.