Having doubts in your project along the way is natural every entrepreneur has that. But saying it in public is PR suicide...
I honestly agree with this and much of what the other critical posters are saying above, but I think most of you are missing one big thing here...
Vitalik is still basically still just a kid!
He was like 19 or 20 when he started working full time on Ethereum, and look where it's at now, with a marketcap of like $30 Billion!
Can you just imagine if your own little pet project that you were working on when you were 19 exploded and within a couple of years was valued at 30 billion bucks, and suddenly you were a multi-millionaire.
How well would you handle it, and do you think your PR would always be spot on?
Whether you like Ethereum or not, for most people there is no arguing that Vitalik is a smart kid. Time will tell if him and the other developers are smart enough to make Ethereum overcome their scaling problems, but I both hope and think they will.