Halo says I need game pass to play physical disk

Even with a ps4 you would need to put this physical disk into the drive to play it. This is how the consoles are setup. Originally Microsoft wanted to do it where if you bought a physical disk once you installed it you didn't need the disk to play the
game. The issue was that the disk would be tied to that console and you wouldn't be able to trade it in. People were upset about that so Microsoft went back to the way it has always been for games.

Did you pick this game up with gamepass when it was on there? It left game pass a little while back and so if you did play it via that way and not purchase it, you would need to buy the game to get access now (either a physical disk or digital download)

If the DLC is not available from selecting "Manage Game and Add-Ons" on the game in the Xbox menu or in the Game Pass menu, then you'd need to buy the game's DLC or find one of the DLC disks that was included in the physical GOTY Edition of that game and
install it.

FYI if you are trying to install from disk you still need the physical disk in the drive to use the game

I've really enjoyed it so far, I got the 3 months for $1. Mostly playing Halo MCC, but I've found I have a few physical versions that i no longer need to insert now, which is kinda nice.

I'm not so much for a voting process for Game Pass, but maybe Games with Gold.