In general I agree with you. I find that most FOSS software is more polished than proprietary software, and it is generally more powerful.
However, I think that one problem that people somehow overlook in my opinion is that the financial side of the issue is also extremely important. I want more people to work on quality FOSS software, and I want it to become socially acceptable to work on FOSS as your main job. For that one thing is needed in my opinion: we as users of FOSS software need to give developers the financial incentives to work on what they love the whole time. In fact I want it to reach the point where immoral, non FOSS companies struggle to find developers because they’re all working on FOSS.
How about using LDAP? It’s a bit complicated to learn but it’s easy to integrate it in a bunch of applications and it allows you to manage user accounts and permissions in one central place.
Maybe try LLDAP which is a modern implementation (haven’t used it myself) which is designed to be simplified and I assume more welcoming to newcomers.