Fedora is like a well-known trade-mark, they have unique logos and backgrounds and so the consequence is to ask why is there no graphical “corporate identity” in the Fedora boot-menu (background, logo etc.)? It’s an easy mean for better marketing and it could play an eye-catcher role. It’s only an idea.
Customization often breaks functionality, I am personally very glad that grub2 is shipped with defaults and no theming.
Moreover, by default (there are exceptions), the bootloader menu is not even shown on a Fedora install.
Exceptions are dual-boot system, or previously failed boots.
Because it is not a corporate os it is made by people and made for people moreover grub theme is not essential and not required at all in fedora it never show you the grub. So grub is not a essential it is essential but in background.
It is better experience when no grub it directly boot into os. I hope you understand.
Now if you want to have a grub theme it is possible you can do it you customize however you want to.
See a os is for just to interact with the application and stuff.
But if you want you can apply the theme and stuff to make fedora like garuda.
In my opinion maybe garuda looks better but the untouched fedora gnome or kde look is elegant.