Implicitly many people, rightfully in my opinion, conflate the utility of a programming language with that language being good. If many people are able to solve real problems with a language, that language is good, the end.
Good does not equal perfect, there is no perfect in the real world of engineering.
There actually are a few measurable metrics of programming languages, but even when we discuss such a simple factor as execution speed that you'd expect to be universally accepted as positive, there will be people arguing that developer time is more expensive and savings made here are more important than the gains on execution speed. There is simply no way two programmers are going to agree in classifying a number of languages as good or bad.
If there is one thing humans love doing is finding small reasons to disagree hah.
I'm sorry, you can't prove a language is good or bad. You can prove it's popular, widely discussed, used by several individuals and organizations, is actively developed, but "good" and "bad" are inherently subjective terms and there's no way to prove it unless there happens to be a universally accepted definition of what constitutes a good or bad programming language.