I think the best middle ground might be where there's a bunch of separate apps that all have their own default server, where they hide most of the fediverse complexity from the user. They'd still all be accessing the same content, but it would just be simpler for 'normal' users.

In the long term this will happen tho. If the fediverse becomes more popular, you will definitely have a small handful of powerful instances (either led by foundations or companies) in the center of everything. That's simply how the internet works.

If you don't like the mainstream, you can join a defederated instance, that does not want to play with the big dogs.

The only way to keep the fediverse as federated as possible, would be perhaps forcing every community and every user to create their instance. This would probably keep even more people away from the fediverse tho.