I don’t expect their exchange rate to be what I see on my app. I expect to pay for the convenience of using US dollars. But I do expect something ‘reasonable'. IMO, their rate wasn’t reasonable.You need to understand that restaurants, taxis, stores, etc that accept a foreign currency in Mexico are doing you a favour and are free to set the exchange rate to whatever they see fit. If you don't like it, that's on you, not them. To expect to receive the bank rate of exchange at a restaurant is a bit much.
But it might be a-ok for you. That’s ok.