I just quoted the investopedia article on fiat currency and even bolded the part that makes it clear that most cryptos are not fiat currency. If it's not issued by a government, it's not a fiat currency. Now, that doesn't mean that crypto currencies can't lose value just like fiat currencies, but it -does- mean that their value isn't determined by said government or the banks that generally create more of it in things like "quantitative easing". This isn't to say that cryptos are by default better holders of value than fiat currencies, but there's also plenty of evidence that some cryptos have been much better holders of value than any fiat currency out there over time.
Now, I will admit that just because some of these cryptos have been great holders of value over time doesn't mean that this trend will always hold. And thinking about it, I think that ultimately, the highest markept cap cryptos may eventually be backed by physical assets. That certainly isn't the case yet, but for those who'd like their cryptos backed by assets, there are some out there:
https://coincodex.com/article/5812/top-5-physical-asset-backed-cryptocurrencies/
Ironically, the strongest of them are backed by fiat currencies, namely the U.S. dollar. The Tether and USD Coin, both backed by the US dollar, come in 3rd and 4th place in terms of market cap, with 66 Billion and 44 Billion market caps, right after Bitcoin and Ethereum. I understand the reasoning- if cryptos are going for a plunge, but you think they'll do better soon enough, I think it makes sense to put your cryptos into a crypto that's tethered to the U.S. dollar, so that you can buy non US based cryptos as soon as the market improves.
But there are also cryptos that are backed by assets other than the US dollar, such as gold, oil (Venezuela's Petro) and even real estate. Some examples can be seen here:
Top 5 Physical Asset-Backed Cryptocurrencies | coincodex.com
Other than Venezuela's Petro, which I'm currently not impressed with, I won't vouch for their quality, but regardless of their current quality, I think they're on the right track. Because while having actual physical assets can be good, they can be a drag. Whether for personal reasons or for business, when you want to send money to someone or some entity that's far away, sending them something like gold is a drag, both in terms of expensive of transport and time it takes for the recipient to get it. Up until cryptos came along, the only alternative was using the banking system. Cryptos provide another option, one that I think will become ever more popular in the future.