The page move broke a bunch of links to the sections of the old page, most prominently to Development policy/Until 2018#Database policy (e.g. Review queue links there). If the instructions there are still valid, they should probably be rescued to their own page.
Topic on Talk:Development policy
Yeah, parts of that definitely shouldn't be a policy or specifically a development, just a guide- People shouldn't approve or vote against how DBAs work or what tickets are preferred :-D, but people should have a way to know how to request schema changes. Maybe substitute the old Schema change ?
On the other side, thing like "All tables should have a primary key" were actually voted and approved at RFCs/architecture committees/office hours: https://phabricator.wikimedia.org/T112637 / Architecture meetings/RFC review 2015-09-16 and while I personally don't need it to be a development policy (and may need review), we need somewhere written on this wiki to say "don't merge, doesn't have a primary key" to back such rejections.
I think the intentions with the blanking were good "let's review all this old stuff", but sadly some people has taking the blanking as "everything goes", and this is causing issues on production.
@Krinkle Because you unilaterally blanked the database section noted above, approved on a RFC on an open session, and didn't suggested a patch in the last 8 months (and being on the receiving end of lots of developer confusion), I am going to create a documentation bug and assigned to you. As Tgr said above, it probably shouldn't be here, but it should be _somewhere_, even if only as a link to wikitech.