I somewhat agree but your time scale is way off.
At least in the US, it’s been exactly this way for at least the last 20-30 years. 20 years ago was 2003, if you showed me this photo and told me it was from the turn of the millennium I wouldn’t bat an eye. The 90s was crazy with all these fast brands and snacks. Everyone’s freezer was filled with totinos pizza rolls.
Arguably longer to be honest. I can’t remember a time where frozen microwave junk food didn’t dominate the grocery stores and TV advertising. I wouldn’t hesitate to believe an argument that it’s been like this since the early 70s but assume it happened sometime in the 80s when the stay-at-home housewife transitioned to the career-focused woman.
I can’t speak for everyone but, in the US, I would imagine students especially cooking with fresh ingredients is pretty rare, especially guys. Personally I didn’t start doing that myself until I was married and really only because my wife enjoyed cooking. Since kids I can’t imagine being on the processed food train - most people I know didn’t start cooking at home when they had kids.
I’m a big proponent of the “cooking is way easier than you think” camp but you’d be surprised how little some people have in their pantry and cabinets. There’s folks that don’t even own a baking dish, anything more than a 12" frying pan is probably a big ask depending who you’re talking to. Spices? I knew kids in college that didn’t even own table salt and pepper shakers… if I said the word turmeric I’d get a funny look.