Back in the day, they had a smaller menu, and if you went at peak hours, they had a bunch of pre-made sandwiches there ready to go.
I want 2 cheeseburgers, fries, and a Coke. They turned around, grabbed the 2 cheeseburgers that were sitting there, grabbed the fries that were already in the bag, filled your coke, and you had a 45 second transaction.
They can't afford to have 5 of every sandwich they sell sitting there. So you have to wait for it to be made. Maybe the quality is better, but eh, maybe not.
Of course back in the day, you couldn't work the counter even if you had bad acne (look it up). Now you probably couldn't hire fresh faced kids for under $25 an hour.
FWIW, I find Culver’s currently to be the closest to an early 1990s McDonalds experience. Brighter, no kiosks (at least at the ones around me). You do have to wait for your food, but they bring it to you, you don’t have to mill around the counter area for 5 minutes.