Hi,
I’ve done the entirety of Halo MCC on Legendary Solo and the achievements for doing so haven’t unlocked.
Why is there new “updates” when the bugs can’t be fixed?
Can’t see your MCC profile unfortunately, but I would double check your MCC service record here on Waypoint and make sure that all games have registered as being complete. It may be that you need to run through another mission or 2 again. As for bug fixing, that’s an ongoing process with patches still being developed. Need to find a balance between fixing high priority issues, low priority issues and features requests