There are great Open Source projects doing fine with the cathedral style, just look at Sqlite and its siblings (Fossil, …).
So I do not see a problem with Ladybirds decision, in contrary, IMHO it strengthens the human aspect of software development and puts the brakes on AI free riders
I still don't see solutions on how a normal person can become a mantainer though.
If all relevant open source projects close up their contributions, you can't enter the project anymore from an external point of view.
Almost all open-source public figures started by being interested in a project and submitting PR to it, until eventually either joining the project as core mantainer or creating a separate open source project. The path is now closed, and I don't see a way in, outside of creating a popular open source yourself