Is the Backrooms alive
This is, honestly less a discussion and just me yapping about my opinion. If The Complex (like that name a lot) is a actually living thing within universe or not, it is in a way its own character.
It has a agenda: Collecting memory, growing. Be it concious or just its nature. Be it a thing that always was or something Ivan Beck made by accident. (honestly I think leaving WHAT it actually is open and never fully explain its creation would be for the best in my opinion)
Clark can come and go as he pleases, because he WILL come again. He will. And IT knows, he can stay there, safe because he wont leave. No reason to trap something if it comes back.
Other PoVs wanted to leave, and that why they got trapped.
Its why in the end (spoilers)