Yes, LDAP is a general tool. But many applications that I am interested in using it for user information. That is what I want to use it for. I'm not really interested in storing other data.
I think you are sort of missing the goal of the question. I have a bunch of self-hosted services like Jellyfin, qBittorrent, PhotoPrism, Metabase ... I want to avoid having to configure users in each one individually. I am considering LDAP because it is supported by many of these services. I'm not concerned about synchronizing UNIX users, I already have that solved. (If I need to move those to LDAP as well that can be considered, but isn't a goal).
The concern is that it would be nice if the UNIX users and LDAP is automatically in sync and managed from a version controlled source. I guess the answer is just build up a static LDAP database from my existing configs. It would be nice to have one authoritative system on the server but I guess as long as they are both built from one source of truth it shouldn't be an issue.