I think distros at least do some stuff beyond repackaging the latest software, namely default configurations (or lack thereof).
For instance, technically Debian has the packages to do SELinux, but it's Fedora (and OpenSUSE, I think?) that actually come out the box with them.
They are also continually improving, if slowly, their package managers to improve the experience of sourcing new software, as seen with work on apt and dnf.
You are right overall that new distro releases have little meaning any more. If anything, I think they are a good method for managing the upgrades to new software; when a release comes out, breakages can be addresses all at once and solved for a couple of years, whereas rolling release requires a person to be vigilant and repair breakages more often. That is not to pan rolling - I use Debian Testing on my desktop. As much as I like newer software, though, I am thinking of staying on Trixie after it becomes stable, as I get tired of applying updates all the time and then something breaking that is incredible difficult to diagnose.