"Over all" is indeed a generalization. He certainly didn't seem to be saying there was no good food here. Since I agree with him, I would have to dispute that it is an "over-generalization". If you search hard you can find decent diverse meals, it's true.
There are, for example, a number of "Mexican" food restaurants here, but the majority that I've been to are all pretty much the same - crappy. Same goes with many other "ethnic" food restaurants, again in my opinion.
Pizza, pasta, parilla. Most restaurants follow this menu - you don't even have to look at the menu to order.
Living here for nearly 8 years, I often hope I can find a really good place to eat something different. I go to a lot of different places.
We went to a seafood place the other day that one of my friends raved about and I ordered a paella. It wasn't even good as just rice and seafood with huge chucks of chicken thrown in - it was completely tasteless.
I've been to "Mexican" restaurants where a burrito, an enchilada and a taco were all the same except for where they put the sauce (on top for the enchilada, inside for the burrito, and no sauce for the taco). They consisted of nothing more than a small tortilla folded over some not-very-tasty meat.
I've been to Italian restaurants and tried a four-cheese pasta where it seems they literally just melted the cheeses together without making a sauce, and the cheeses were in the process of separating as I tried to eat my meal.
I've been to expensive steak places in Puerto Madero and other places where the meat I got was tough, full of gristle and dry as a bone.
To me, "over all" is not at all an over-generalization (nor hyperbole), but rather a statement of fact for people who have discerning palettes. It's not impossible to find good places, but the majority of places that serve bad to so-so meals is much greater, to me, than those who serve good to excellent meals.