Some extra measures came up for a reason if I remember correctly. Some time ago the Ubuntu Wiki became Trolls and Spammers Joy. For that, Admins took some extra security measures like Ubuntu SSO and immutable pages.
The Wiki is community maintained for a long time. I’m not sure if Moin-Moin is the best option, but this cannot easily change, I mean without data loss.
Either way, even if the Wiki is closed/moved at some point nothing should be deleted. It includes tons of contributions from community members and this must be respected.
I agree it is not in its best shape though.