Maybe by leaving you'll indirectly be helping them get the push they need to start look for something better themselves.

I know I dragged my feet but eventually enough people left that I was like, "Alright I have to find something new" and I ended up with a much better role and compensation as well, and probably should have left earlier. And I also like the people at the new place too, and keep in touch (somewhat) with my old coworkers.