I just don't see the draw of immutable distros for non power users.
With traditional ubuntu/mint/fedora you have 15+ years of forum posts, tutorials, and community wisdom to help you out if you get stuck. You probably wont need to, but it's nice to be able to just google something and get a dozen good answers. If you want to use containerized apps you also have that option.
Also depending on your taste in gaming, you might need access to stuff outside of steam/lutris/heroic/flathub. In those cases getting your game working could be a bit of a hassle compared to a traditional distro.
I totally see how immutability can be a draw for tinkerers and developers, but for regular users it's solving a problem that doesn't really exist, or is pretty rare if it does.
I also think there is something to say for picking a distro that's been around a long while. Hopefully Bazzite is still around in 10 years. I feel very confident Ubuntu/Mint/Fedora/Pop! still will be.
That said, I'm glad to hear you and your friend are happy with Bazzite. It seems like a really good option if you only play games from steam/heroic/lutris/flathub. A best of both worlds between a PC and a gaming console.