Mastoot is about as simple as the official mastodon app. If you don’t want to do anything complicated, you can’t go wrong with either of these. However, if you’re like me, and you don’t care about people, but you care about topics, these apps are going to be useless to you. Following particular hashtags just doesn’t work with these.
Agreed, it’s definitely on the pricier side. But in my opinion it’s also the most refined one, the app works great and the UI is really good. If you appreciate well-crafted and -designed apps, it’s worth it. If those things don’t matter as much (or if you simply prefer to have more options/customizability), it might not be for you.