Ubuntu has fallen out of favour with quite a lot of Linux recommender sites and reviewers and its mainly about flatpak and Gnome, but also gaming support by default. Other Linux distributions do things better now for the influx of gamers to Linux and with SteamOS being on Arch a lot of Arch deriatives are becoming increasingly popular. I don't think its Fedora picking up users, its Cachyos and Bazzite.
What are the specific issues with gaming that you're claiming Ubuntu has?
I've been using Ubuntu for a few months, and I have complaints - lots of them. But gaming isn't one. I just installed the apps I needed and they worked.
Isn’t Bazzite based on Fedora?
Linux distributions shouldn't ship with Steam installed and imho bundling it makes a bad precedent.
Steam should be easy to install (whether from a store like Flathub) instead.