It is pretty unfortunate that so many people used "PostgreSQL" and "Postgres" in their module name and DBD::Pg didn't, so it gets ranked lower for those queries. But ranking is a hard problem when there is no curation. The MetaCPAN team does want to improve this if possible.
As for DBI, it's definitely in the "stable" category and isn't trying to keep up with anything; the DBD::Pg driver though was last updated this month.
I'm sorry your initial search for a term didn't immediately give you what you're looking for, but the database layer of Perl is very mature, and if you looked at the docs for DBI, you would see that it uses drivers in the DBD namespace, and if you search DBD, postgres is in the first few results, under DBD::Pg. Just like NPM, having a word in your module namespace or description is probably not always very well correlated to module quality or whether it's actually related to that term, so a bit of active research is best to determine what should be used. Then again, I'm not sure NPM is known for providing mobile namespaces that allow third party modules to interact well in a pluggable way, which is quite common on CPAN.
Often I'll just not find the library I want since nobody using that tech is actually writing Perl. For example, complete lack of a working GraphQL package until late 2017.
CPAN search in particular is unbelievably bad. The first result for 'Postgres' is a package last updated in 1998 (not joking), try to find a usable driver here: https://metacpan.org/search?q=postgres. Even the widely used DBI package has last seen an update almost a year ago.