If he’s getting to the first round of technical interviews then it’s likely not a languages issue. That’s the round that many companies put you in front of a mid-level dev who arrogantly asks you a code-kata question and refuses to answer questions. It may be that he’s not inherently good at solving the toy box problems on the spot. That’s the issue I tend to have in these rounds.

Though I guess it could be a languages issue if the mid level dev doesn’t know the language you’re doing the problem in and marks you down for that.