The game is basically multiplayer first and campaign is really more of a side perk. One of the drawbacks of being multiplayer first is if there aren't enough players doing ladder, then the ladder system can't really do its matching job well and players at low levels can't ascend rank.

Think of forced ladder matches as an incentive to not hide in campaign. Most seasoned players will tell you that if you really understand the game, early ladder isn't all that bad. In fact, my experience as a first time player was long streaks for long periods - something I kinda miss as a rank 1-5.

I do think there should be more multiplayer options so it becomes more palatable to new players rather than a tyro charging into an inevitable curbstomp, which it sometimes feels like. Balancing the multiplayer system to be more fun should be the priority over segregating it from campaign mode.

Spoiler