I am signed in as an admin user of my instance. A different, non-admin user has created a community on my instance. I can’t edit this community’s details. If I create a post in this community, I can’t use the … menu to assign myself moderator of this community.
What do I need to do to give myself access to edit this community?
The point of being an admin is that you can edit and change everything that is posted. If someone does something illegal on your instance, or they’re posting stuff you don’t like (racism, homophobia, etc) you need to be able to fix it.
Admins have always been able to modify posts. See Reddit, forums, etc.