If the government considers the value in crytocurrency for sentences, it will have a hard time justifying that you must pay your capital gain the the fiat currency of the country and not in the crytocurrency in which it was made.
That doesn’t mean that when you make a profit selling potatoes that you can pay your taxes in potatoes.
What I dont support is taxing when switching in between crytocurrencies. Which in the analogy would be me exchanging my potatoes for carrots. Imagine if I had to pay taxes on my exchanged potatoes while I didnt make a dime on that.
That said, I agree it's frustrating that you are liable for what are unrealised price changes (IMO it's not profit until it's in the bank).
In the United States and in many other jurisdictions, if you realize a profit through commodity exchange, you owe tax on the fair market value of the exchange.