4K content on streaming is pretty terrible - so I can’t blame you for that opinion.
But comparing a 1080p Blu-ray to a 4K copy makes it a lot more noticeable, akin to watching a 480p DVD next to a 720p Blu-ray.
Lines are crisper, you can notice a lot more detail (skin texture on close-ups), background objects are clearer - nothing exactly revolutionary, but still an improvement nevertheless!
Again not the original person you asked, but I found Bazzite a tad too restrictive - I couldn’t for the life of me get PIA’s VPN client installed (for all of those Linux ISOs on my home server).
Ended up switching to CachyOS, which is also very gaming-focused (and Arch-based, if that matters at all!). It’s a bit more open, allowing you to fiddle (or not) with everything a bit more than Bazzite.
As an aside, my only hang-up is that it sometimes hangs while trying to boot up the GUI (not sure why, hasn’t bothered me too much), and it can’t wake from Sleep - but I’m pretty sure that’s just something misconfigured in the BIOS.