I personally haven't played online much because I'm not that good of a pilot and as soon as I take off I get shot down. Playing off-line is easier, more enjoyable and more comfortable for me but after a while it gets old because AI in IL-2 (and even the old series) is not very well programed and is mostly predictable.
In the long run, I would want to fly online more because combating humans is more fun than shooting down AIs, i'll just have to get better.
The idea of campaign is not very appealing to me because you are gonna be doing the same thing: flying the airplane, no matter what campaign you're in, or what battle you're fighting. It's not like a campaign in a strategy game where u do very different things for different situations. So campaign maybe good for a little bit, and I'll still end up in the hyperlobby.
I think the devs are on the right track focusing more on multiplayers.