Personally, I don't want crossposts from a whole other site. At that point just copy their own link and post it here. Unless your goal is to give Reddit even more traffic. If we were just to copy (steal) their posts, it would be enough to keep me here.
I was on Reddit for news. Whether it's mechanical keyboards, monitors, anything tech really, a game I play, new homekit devices or a new protocol, Apple stuff, streaming stuff, movies, sports or regular news. Sure I also did google some odd questions from time to time that would lead me to Reddit but it was far from my primary purpose. So for kbin to be a viable solution I just need people to buy into this. To start posting here instead whenever something happens or releases within one of my hobbies.
For now I use both but I'm much less on Reddit. I used to read a book every other day but I've considerably slowed down within the past year so most of the time I used to spend on Reddit has been spent elsewhere this past week.
On research and research-adjacent subs it's pretty common for the poster to make a text post with a link to a paper, quote the part of the abstract or conclusion that actually contains the new/important part, and then maybe add a bit of their own commentary about the significance or new questions it opens as well.
Those are the sorts of cross-posts I'd like to see. But if it's just a link or a meme, there's no real benefit.