Some people thinks he wanted to FUD. I think his goal was not to FUD but to inform. With the popularity of dPOS blockchains it's important to know all the downsides. It's easy to think that it's the Holy Grail because of the high Transaction Per Seconds and fast confirmations but very few people know all the technicalities to understand the traps of such a consensus mechanism. I believe Vitalik is one of the most brilliant people (and humble!) in the crypto space so I value his input and I think he should not be taken lightly. Just my opinion.