First and foremost - they're always in parts of the country that are torn by poverty but OMGz look at the beaches. It feels gross.
Secondly - the food is BEYOND trash. It's garbage. My stomach took a week to recover.
Last is this point up above. They very clearly replace alcohol with god knows what to save money. I was in Mexico 2 years ago for a friend's wedding (never again), and the alcohol always tasted off. It also didn't really seem to work in the same way - I could drink 10 margaritas and barely feel a thing. One night, after drinking wine, I got violently ill in a way I hadn't before or since. I thought at first, MAYBE I just overindulged and this was a hangover or something - but it was not.
Shortly after I found out a few tourists had died and they'd seized thousands of liters of bootleg liquor in the same region I was staying in. So yeah, fuck these places for putting their guests in danger and taking advantage of the locals and their poverty. So disgusting.