I don't really dislike primaris other than the phobos units being too tacticool.
But I do feel like they should keep 40K as it is with mirrored terrain etc as a containment game for competitive autists but do a Warhammer for Adults variant where you get 30-50 guys, 1-2 tanks, and 1 commander. And fill that mode up with random event tables, NPC aliens/monsters, complicated scenarios, and other stuff the competitive dorks will hate.