TLDR: Give it some time to load, its 98+ gigs of data.
I bought the disc version of MCC waaay back when it was new. Never had issues then. Stopped playing after a few months until Reach was announced.
It froze after hitting start every single time. I've uninstalled/reinstalled both with and without the disc installed (I now have Game Pass), still no luck. Then I had a 90's gamer moment: let it sit for a few hours while I'm out to let any updates load, as this monster has gigs of updates, patches, and whole games added onto the original game "frame"
Well that worked. I was gone about 30 minutes, so it was fairly quick. Came back and it was on the menu screen. Every game works fine. Not saying it's THE guaranteed fix, but it's a thing that did work.