I don't interpret the quote as meaning "if you can't do it don't criticize it". It's just saying that it's much more noble to attempt to do hard things and fail

I don't interpret the quote as meaning "if you can't do it don't criticize it". It's just saying that it's much more noble to attempt to do hard things and fail, than it is to do nothing but take cheap shots at those who are trying. In this context I think it was more a reflection on the cheapness of the shot and what it says about the people making the cheap shots. There's a big difference between honest criticism and "your thing sucks, haha!"