Maybe not dumb but I've definitely been forced to at least partly learn a few terrible languages so I could use some system:

• PHP so I could write custom linters for Phabricator. Pretty successful. PHP is a bad language but it's fairly easy to read and write.
• Ruby so I could understand what the hell Gitlab is doing. Total failure here, Ruby is completely incomprehensible especially in a large codebase.
• OCaml so I can work on a super niche compiler written in OCaml. It's a decent language except the syntax is pretty terrible, OPAM is super buggy, and I dunno if it's this codebase or just OCaml people in general but there are approximately zero comments and identifiers are like ityp, nsec, ef_bin... The sort of names where you already need to know what they are.