Exactly this. Mastodon seems to still focus on the community aspect of federation, yet few people want to have one or a few interests/groups. Decentralization is a great idea for operating, but I’ll never see the point of a “node” where I have more interest in interacting with those on the node than with others.
The first may be a Ruby on Rails problem (although I am not sure), possibly exacerbated by the decentralized layout of Mastodon instances. The second seems to be a fundamental design problem.
It seems to me that the original idea of Mastodon was that people would want to participate in communities that focus on specific themes. Many instances are aiming to serve people who are interested in one particular thing. Because of this, finding people and posts on other instances is harder. But reducing my interests to a single dimension is not how I used to use Twitter, so this is a major usability problem for me.