Let's go step by step: Gambling is putting down money in a game of chance, that is divorced from physical reality. It contributes nothing to the real economy, horse races do not provide any goods or services. Like horse racing or slot machines. If the US economy collapses, slot machine works the same way.
Value of Bitcoin is providing a real service that functions, payments. Etherium provides computation and used to power crypto-kitties, etc. It was operating for 14 years and it's security functionality is proven. You might think it's function is crap, but that's a separate argument. If Visa and Mastercard collapse tomorrow, that would have a dramatic effect on the value of crypto. If a major government adopts it as a national currency, that would have an effect to.
Therefore it is very much like investing in a startup. Now, the individual people investing into it might have no idea how it works, but how is this different from idiots and speculators among retail investors - Elon Musk tweets about Signal, and value of Signal Advance, a totally unrelated company, goes up 1,100%? That's not gambling but bitcoin is?
I am certain that most of the folks here calling it gambling are not objectively sceptical, they are very salty.
I have accepted things for what they are, I mined my first two bitcoins, spent them on beer at a funky pub in Prague when it was worth $50, and never touched it again. People in the community ranged from anarchists to bankers, and they were more passionate about their work than any startup founders I've seen. I am not envious of them and I don't call them names, I appreciate that they've introduced something completely new to the world even if the outcome is a bit questionable.
NFTs on the other hand seem to have no merit behind them whatsoever, or at least so far I could not see it.