That's an extreme straw man that trades a lot on what a "critic" is.
Martin Luther didn't criticize the papacy because he doubted the papacy's capacity to realize its ambitions. He criticized the way the papacy was then operating.
People holding forth on how something can't be done are best described not as critics but doubters (or haters). "I can't imagine a way to do X, therefore X can't be done." How many impossible things does Musk have to do before people take serious Musk's ability to realize his visions?
Hating is so easy. But today's capacity to develop technology is utterly unprecedented.
Lead. Follow. Or get out of the way.
We're talking about strawmen: nobody is saying that. Nobody is saying it can't be done. They are saying...let's wait until it is done, because right now it's just a video. Is that hating or an entirely reasonable stance to take?