I guess there could be some sort of "super node" solution, where a known Mastodon server would just forward you the "what happened while I was asleep" stuff and I guess people could encrypt their messages to you with your advertised public key, so that you don't have to trust the super nodes, but I am not sure about the additional complexity involved in implementing that vs current Mastodon using ActivityPub, nor about the usability challenges involved.
It's actually remarkably easy to onboard to SSB with Patchwork. The problems set in when you start considering mobile devices or multi-device support (the latter is currently possible but risky).
For example, in Freenode you don't control what gets downloaded and served (which also helps to hide what you're fetching on purpose).
Same with federation: It's what you need right now for "normal" users (e.g. compare user numbers of Mastodon etc to purely p2p alternatives). While I personally self-host a lot of stuff and would be willing to run a Mastodon instance for friends and family, I can't expect or even recommend they run something themselves individually. Thanks to federation, nothing is stopping those that can to run their own single-user software speaking the protocol, or for instances to only serve very small groups.