Larian doesn't think this is a game to be played with a random guy you don't know.
Campaign mode, I'm totally in agreement. I wouldn't dream of starting such a large-scale match with strangers. Once-off skirmishes, on the other hand, seem perfect for casual multiplayer as they'd be in that sweet spot of 10-15 minutes and are fairly lightweight and focused.
I don't mind small multiplayer communities. In fact, I kinda like it when there's only a few hundred active players and you actually get to know the regulars who play in the same time zone as you.