When Amazon started, people said nobody would buy what they couldn't touch. The iPhone got the same treatment for ditching the keyboard. Early Bitcoin was a scam until it wasn't. Those three are worth trillions now.
Pessimism is a great way to sound sharp. You list the risks, cite the failures, and most of the time you're right — most ideas die. Sounding right is not the same as building anything.
Optimists are usually the ones stuck in the mess trying to make the thing work while everyone else explains why it won't. That bias toward action is boring to watch and hard to argue with after the fact.
Criticizing is easy. Shipping is not. If you fail nine times and the tenth one hits, people remember the hit. Use that.
Short term, pessimists look correct a lot. Long term, the people who kept building own the outcome. I'd rather be wrong in a draft than right in the comments.