Wanna see a good example of what the RTS campaign always should have been? If you haven't, play Dawn of War 2, it's a case study on good design decisions.
Man, I hated DoW II, frankly. DoW I was a classic RTS heavily influenced by Kohan II; it was fun to bash AI with all day long.
DOW II made for fiddly micro and the campaign was pretty lame; I didn't enjoy it very much at all, and skipped DOW III entirely because it looked like more of the same. I get that, for some people, building turtle bases or rush-stomping AIs that cheat isn't actually all that fun, but honestly, I like RTS's where I get to queue, crush and consolidate, so long as the actual micro of the fights is fun. I could care less about MP, too; and yes, the research says that's been a huge and under-served audience in the world of RTS design in general, ever since StarCraft and DoTA showed the industry that they could make ridiculous amounts of cash on MP sometimes.
DOW II felt more like an exercise in save-scumming, because you just weren't going to recover if anything went horribly wrong, and that's kind of boring; I'd rather lose after a series of desperate comeback attempts than be like, "oh, it's 5 minutes in and I missed that one invisible scout unit that's just wiped out my irreplaceable unit". I get that that's a matter of taste, but the sales figures pretty much speak for themselves.
Between making the completely tragic mistake of not wholeheartedly supporting modding for DOW II (and III, from what I read, is even worse) which was pretty much betrayal to their modding community for DOW I, which was expecting a much-more-open engine that time around and their designs, THQ pretty much ruined a perfectly-good game series by continually forgetting that their core fanbase didn't want radical experiments in game design- they wanted more giant hordes to smash around with.