Mbin isn’t nearly as egregious as piefed in the way they introduce breaking changes to the network.

Is Mbin updated much?

I’m not assuming anything, it’s been stated repeatedly. Rimu could implement his preferred features in ways that don’t degrade the health of the network but chooses not to.

Have Lemmy mods approached Rimu at all?

I’m not sure what relevance that has, but you can count those instances on a hand missing two fingers (i’d note that dbzer0 does not defederate from 2 of the three that I assume you’re referring to, nor would I advocate for it). It would be interesting for someone to map out just how much of the fediverse is effectively being defederated for piefed servers with large user block lists - i imagine it’s quite a large chunk, especially when the most popular users to block are the ones producing the most activity. The larger those servers grow, the bigger those holes will become.

Just noting that there are already holes of communication due to defederation (hexbear/lemmygrad are pretty medium sized).