Who is claiming its impossible is what matters as well as when. If somebody has given something serious thought then their claim could be valid but unless they're providing any evidence it's probably a worthless claim. The evidence is also time constrained as the US going to the moon right now is pretty ludicrous but in a few years maybe somebody will have made a new lander.

Also I don't think you picked good examples.

Uber wasn't the first taxi app so it was definitely possible (IIRC both mapquest & google maps had a taxi tie-in at one point). Amazon used to charge for shipping so the cost of pack & ship is irrelevant (they weren't doing the current VC model of giving out dollars for 50 cents). See https://press.aboutamazon.com/news-releases/news-release-det... .

Personal computers were ludicrous at a time when a computer took up more than a whole room. Just like flying cars are ludicrous but technology changes and thats why due diligence matters, is this company developing any technology or are they lieing.