How to play purchased game on multiple accounts?

So I purchased the Forza Horizon 5 Xbox series X edition for Christmas. My fiance went through full set up yesterday and enjoyed playing his game! I was also kind of excited to play around with it, but did not want to mess up his game play. I created a separate account and tried playing. The first round it told me that I shouldn't open the game because his account had a quick resume set up. So I went to his profile to check it, figured out how to save the game and went back to try and open it on my account. Now it tells me I am not able to open this game because my account isn't the one that "purchased" it.

I'm extremely confused because I've been under the impression (for my entire life) that when you purchase a game on any console that it would be able to be used by any account on the console. (I can understand that maybe I wouldn't have access to any online functions, or possibly like DLCS). Why does it seem like this is not the case? Is xbox and Microsoft looking to scam even more money out of their consumers by forcing them to purchase a new download of each game on each account?!! Not to mention, I spent a pretty penny on this bundle, under the assumption that it generally came with the game, not just for one person. If I knew that was the case, I would've bought everything separate including the game because maybe having an actual physical copy would work for multiple accounts.

If anyone can help, it would be greatly appreciated. I am beyond frusterated about this if I am correct on how this works.

:)