No it isn't... You can buy just about anything with any of the world reserve currencies. You can also pay taxes in the applicable jurisdiction with any government currency.
Buying something with a currency, and paying taxes, are both other people buying the currency off of you. In one case they're buying your currency with goods and services, in the other they're buying it in exchange for protection. McDonalds gives you burgers because they want your USD. They want your USD because everyone wants their USD. That's how fiat works; the biggest difference between Bitcoin and USD is that Bitcoin is deflationary, while USD is managed by a central bank.
World currencies regularly collapse. What people fear might happen to BTC has already happened to the Zimbabwean dollar, the Argentine peso, and many others. It even happened to the denarius during the crisis of the third century. Even with stable currencies, there is plenty of risk to be had in FOREX trading. So... saying that BTC is a lot like every other fiat currency is not so much a complement as it is a neutral observation.
It isn't about potential for collapse, and even if it was it is far less likely that the USD collapses tomorrow than BTC does...
USD, Euro, Yen, etc. are all far more useful as a medium of exchange than BTC. I would argue that their primary usage is just that - a medium of exchange.
Until you can buy most useful things easily with BTC it is not like fiat.
Lastly, if BTC or any other crypto was to grow to the extent that most people were willing to accept it in exchange for goods or services, I believe that governments would be incentivized to shut it down.
I promise you, if I showed up at my corner store with a EU50 note and said "Would you give me a gallon of milk for this" the dude would take it.
He probably wouldn't give me change, so my effective exchange rate for Euro->USD would be something like 20x reality, but you gotta pay for convenience.
World currencies regularly collapse. What people fear might happen to BTC has already happened to the Zimbabwean dollar, the Argentine peso, and many others. It even happened to the denarius during the crisis of the third century. Even with stable currencies, there is plenty of risk to be had in FOREX trading. So... saying that BTC is a lot like every other fiat currency is not so much a complement as it is a neutral observation.