Indeed. The default repo config does define mirrorlist. The defined Rocky’s HTTPS-server returns a list of URLs to repo mirrors near you. The baseurl would force your system to use only one URL. That points to dl.rockylinux.org by default, which is under heavy load because mirrors are syncing from it too (as 9 is new).
The mirrorlist offers better performance and load balancing. If you must use fixed URL, then pick a mirror near you.
As for editing the config files, the dnf config-manager might be cumbersome, a configuration management system (e.g. Ansible, Chef, Puppet, Salt) would be awesome, but for dirty hack sed is “fun” (unless you end up in tears).