I know you're discussing chain restaurants and not fast food, but I can confidently say the last time I ate at a McDonald's, Burger King, KFC, etc. was during the Clinton administration. Fast food is terrible, and it makes me feel bad for having eaten it. I have made the choice to avoid those places, it's easy.
As for chains, most have been bad - serving pre-packaged and reheated product - for years. And as many here have mentioned, when you dine there, you are giving money to huge corporations instead of locally owned businesses.
A friend asked me to meet him at a Panera once, not too long before the pandemic, and it was a terrible experience. All the ambiance and quality of a high school cafeteria. I don't intend to ever go to one again.
I live in Southern California, and I am stunned that places like Taco Bell even exist here, because you would need to drive past a dozen great honest real Mexican taco places in order to get to one.
But I think the reason people do like Taco Bell (and chain restaurants) is that no matter which highway exit you take across the country, the experience will be the same. They are repeatable. So for people who want Chili's, every Chili's will do. Same for Panera, Olive Garden, etc. If you don't want to have to worry about having a new or different experience, you go to a chain restaurant.
And sadly there are lots of places across the country where the predominant kind of restaurant is the chain. The food tends to be mediocre at best, it's overpriced and the whole place is pretending something it's not.