Ahh, but that is customer mentality you display there. Not business mentality. You think in net profit, like selling from customer to customer in a yard sale, yet you have to think in gross profit.
A customer's payment is net for the customer (+ vat where they do not add vat before checkout).
That payment is gross for the business and there goes away all the fees and taxes till it becomes net income, that in the end would pay your salary.
As for taxes themselves, feel free to point out a system in history that worked better. At least we now mostly have percentage based taxes. A society as an entity needs funding. You can of course rightfully complain about the specifics and about people abusing it. Or you can try to boycott certain national systems. But if you want to boycott US system, you better not sell on an US platform.