Debit cards aren't that, in practice, because as you say they typically get the same 3% fee whenever I've asked. Toast and other point of sale networks just charge it based on the network and not the card type.

But even so, I still prefer the credit card instrument, used as a "charge card". For those that don't know, a "charge card" is common with businesses and is expected to be paid off every month. But it helps with managing your cashflow - e.g. you can keep your money in a savings account all month and make one transaction at the end - and it keeps your actual money from being at risk of fraud.

Most Europeans seem confused with how Americans use credit cards for everything, but about half of us use them as charge cards, paying them off every month.

That is a benefit, so I can see paying a small percentage for it, but I don't think that benefit alone justifies the 3-5% of a transaction that credit cards charge now.