I'm worried that multiplayer will get repetitive quickly

Call this heresy but even though there will be some variety of stuff to do, I think that the numbers of active players will drop massively in a short time. Don't get me wrong, I've been waiting for this game for the past 12 years and I expect it to be the best game I've ever played. Already preordered Ultra edition. So am I the only one that is a bit skeptical about online modes? Like how many times we would have to do exactly the same mission with the same scenario to get a new cosmetic right? I would love to put hundreds of hours into this game, but I think that after say, 20-40 hours you will have done everything.