I don't think the people who became millionaires through cryptos agree with this statement. but afterwards it is of course easy to talk. the question now is of course whether it is still profitable to invest in bitcoins at the moment, for example. I would say yes. still is some kind of gambling, but that is the wonderful thing of live.
The number of people becoming millionaires by trading cryptocurrencies is pretty limited and only a small percentage of people are able to make it that far to be honest, it really takes dedication to fail so many times and still try again and again in order to become consistent in taking profits from the cryptocurrency markets which are extremely volatile and unpredictable to any untrained eye. Investing in bitcoin is not a gamble if you ask me, it is really a good place to invest your money rather than investing in a property or any other kind of High yield investment, bitcoin is risk free and a safe investment according to me.