I think there is a place for productive criticism, and asking questions like "Why is it so hard to scale 4chan?" or "Why couldn't Amazon keep their cloud service online?"
But the key is you must be asking the question to learn, not just to ridicule. The intent can't be just to say "I could do a better job if I was doing it" but to discuss what shortcomings are there or improvements could be made with the goal of learning.
All true. And if you say "I could do better..." and it is in a remotely profitable field, perhaps you should be doing just that. Much of innovation happens because someone said, "I could do better" and then did. Nothing good came of people saying "I could do better..." and then watching TV.
But the key is you must be asking the question to learn, not just to ridicule. The intent can't be just to say "I could do a better job if I was doing it" but to discuss what shortcomings are there or improvements could be made with the goal of learning.