You actually did not give strong reasons why cryptocurrency can't replace fiat currency. Cryptocurrency can actually/theoretically do most things fiat currencies can do, but I doubt typical fiat currencies can safely do most things cryptocurrency can do with losing their centralization. Besides, government can run their fiats on Blockchain or other real decentralized system.
Crypto could actually work better in rural areas than fiat, even without relying too much on internet. But I believe safe/crypto-friendly worldwide rural internet coverage is a possibility in the future
I still agree with the author, that crypto cannot replace fiat money. and I have my own reason by what I'm actually experiencing in this market. In the past, I was just a bounty hunter and didn't want to learn about the crypto trading market. But as the campaigns started to dwindle and shoddy, I tried trading and realized it was a very tough field.
The news that crypto can replace fiat, a lot of good news about crypto but have you seen it widely applied in technology countries yet? Totally a zero!
There is no growth in payment services and there's no reason people change their habits to use a coin that has a very high volatility in minutes!
The opinion that you are agreeing and believe that the future of the world will use crypto, you should reconsider. After being more experienced in this market and being passed on by many predecessors, my conclusion for the crypto market is MANIPULATION! My advice is to stay away from the good news on Twitter, sharks will swallow you anytime you fall into its trap.