> I'm pretty sure every time I have learned a new programming language I came away a better programmer.

You might want to think a little bit about the fact that you are predisposed to believing that your efforts are not wasted.

If you spend the time to learn a new programming language, you're then predisposed to believing that it wasn't a waste of time, and are thus susceptible to confirmation bias, which causes you to ignore all evidence to the contrary.