So many people are having a bad first experience with Mastodon because they're using the official app which is lacking features, doesn't allow image uploads randomly, has random slowness, and doesn't give you easy access to the two most active feeds where you can find people (Local and Federated).
Please switch to Metatext, Tusky, or Tooot for a better mobile experience (or even use a browser).
Out of the >15k users that joined this week, over 11k are on the official apps.