Legally, that's irrelevant and "using another channel" without paying taxes is still tax evasion. You buy a thing, the seller has to pay value added tax. For digital goods that's hard to track, but it still applies. If you buy pizza with your coins, that pizza joint has to pay taxes on that sale.
The involvement of a credit card company has absolutely no influence on this situation.
It goes further. You and the seller, when exchanging coins for real money might face additional taxes, if the coin changed worth.
There are many, many reaons, why coins are a terrible idea. I get the desire to have something independent. But having an alternate currency does not exempt you from laws regarding payments, taxes and all things regarding money.
Imagine paying with gold coins. Real, metal coins. Do you think the business you buy from would not have to report the sale and pay taxes on that sale, just becaue you paid with valueable metals?
But maybe there are things lost in translation. There are fees from credit card companies that are not taxes, but fees. Taxes are what the governments want. Fees are payment to the credit card company for their services. The fee for a bank to bank transfer internationally is around 20+ dollars. The fee for a bank to bank transfer inside a country is typically near 0. The fees for services like credit card companies and paypal are roughly 30 cents plus 3%.
Oh, and there are fees for a transfer inside a coin system. It's what's supposed to keep the coin alive. Those fees ain't cheap either. Fees won't go away, just because you use crypto.