Just wondering out of curiosity.
Topic on Project:Support desk
our oracle and sql server support was pretty bad, nobody was testing it, and there werent enough people willing to maintain it. See also https://phabricator.wikimedia.org/T191231
Hhvm has decided they wanted to remove support for references, which mediawiki needs. https://hhvm.com/blog/2019/10/01/deprecating-references.html