The admins (of other sites) who chose to disallow immediate topic creation were almost certainly in a fight against spam. It’s common for a spam account to post a new thread.
It’s possible that these same sites have some kind of “introduce yourself” thread, or category, where a new member is expected to say something about their interest in the subject matter of the site: that can help to build community, as a person has an introduction as well as their other contributions.
If you find a discussion site seems to have hostile settings, it’s probably because it has a spam problem, or a flamewar, or a sock puppet problem. Try to see things from the admin’s point of view, and try not to be part of their problem.