That collection is the same as the four games. And if you doubt 343 will spend time fixing the issues, the proof is already against you. They've been working around the clock releasing updates that, for a while, didn't help. But now? Now the problems are mostly fixed. 5% of the population still has issues, but the rest have been finding games just fine with only a few tiny bugs.
I did underestimate the time it would take them to do this. But it's worked for the most part and I fully expect it will continue to work until the remaining 5% can play matches too.
Oh, and the Halo 5 Beta matchmaking is oddly working perfectly for everyone including the people MCC's been screwy for. I don't know why that works flawlessly and the rest still has some bugs, but hey, it's perfect matchmaking to the same degree any Halo has ever been. And it's a new experience that will let you give 343i feedback on stuff. Go for it. I do want you to have your fun.
On the note of not buying the collection to play "old campaigns" each one's been updated in lighting and water effects, given new achievements and easter eggs, and Halo 2 in particular has been given a complete graphical overhaul to the point it stands as the best graphics you can get on a console, and that's in gameplay. The graphics in cutscenes are elevated even further. Even if you couldn't find matches at all, the MCC's campaigns alone offer enough new experience to keep you busy a few months. Not a single one is truly an "old campaign" because it's been remastered to provide a superior experience. ESPECIALLY Halo 2.
If, between the MCC matchmaking in its current, albeit somewhat flawed state, the perfect Halo 5 beta matchmaking, and the four campaigns with all the new content they have to offer, you cannot have fun with the MCC, it's not that the game is boring: it's that you are.