It's not charging people have issue with, but the initial subscription model approach to ads it took.

It might have worked for Reddit with its api calls they were charging for and the space of reddit generally being full on monetization of its users, but for something related to the fediverse it was off putting. And I think people here are more adverse to ads even being present in an app than paying.

Approach to subscription requests I've found best has been Christians approach with Apollo of having no ads but less features on the free version like limits to filters, no multiple account logins, and no submissions.