In an interview/blog I read, Josh Holmes said somewhere that joining a game in progress would be disabled across all matchmaking game types (excluding war zone). Why was that important? I've been playing halo casually since 2009 and not having new teammates join your game when one or two leaves can be frustrating. In MCC, it is almost guaranteed that I will not finish a game if two out of four of my teammates have quit. Why not have a couple unranked playlists that allow join in progress? I'm sure warzone will be a blast, but not having join in progress when you're thrown into an arena game of complete strangers is not a fun experience. This is especially true when the "skill matchmaking" system pairs you up with people who are much better at halo than I am (which is probably 75% of the halo community, unfortunately). I am aware that customs, forge, and even campaign will have join in progress, which is great.
Arena - Why is join in progress removed?