He has a subtler point:

While learning languages X and Y will make you a better programmer in the long term, due to the added perspective they give you, keep in mind that this experience doesn't necessarily apply immediately and directly to every language you work in - don't try to force alien idioms from your new language of fascination into your day-to-day work language, because it's probably a much greater stretch than you realize. It will instead make your code incredibly awkward for everybody else to maintain, actually making you a worse programmer. (This is my understanding, but speaking as someone who has been guilty of doing this in the past, it's really something to be mindful about.)

Update: I probably should have made it more obvious for some people that the title of the post is not entirely serious, and mainly I'm just griping.

Or you could have titled it "Why using X makes me a worse software engineer" seeing as that's your conclusion.