Can we just... not?

Create your own community and generate new content organically rather than copying and pasting from somewhere else. Some people left that joint for a reason.

Already exists at lemmit.online. Many servers block it because it's annoying. I use it to keep track of niche communities I left behind.

Mirroring Reddit threads discourages participation as the OP isn’t there and there’s little point in discussing with yourself.

It's been tried. It sounds like a good idea but all you get are a bunch of threads with no comments and an OP that can never reply.

There was even one that spun up a Lemmy account for each reddit user that they could claim to ease the transition.

While a cool concept it was largely derided by the existing threadiverse users.