I grew up in the 1970s. Spaghetti wasn't considered to be a weird foreign food at all. It was available in all supermarkets and was pretty much the standard meal served when a friend came round for tea after school.
Yes, if the oven was turned on it was filled, so a rice pud, or scones, pie or crumble was made to use up empty space. People had far less money than they do now. Electricity was expensive. The heating was only put on for a few hours in the evening, and definitely not over night. Strangely people made far less fuss than they do now, and didn't consider themselves to be deprived.
Meals were meat and two veg, always spuds, and whatever veg was available from the garden. Puddings were for Sundays, when we always had a roast. We shopped once a week, as supermarkets closed at 5pm, so if you worked you couldn't shop afterwards. Towards the end of the week things started to run out, so you made do with what you had. Meat always came from the butcher, never the supermarket. It was probably better quality but we ate less. A steak was 4oz. Now if you go to a restaurant the smallest steak you can order is 8oz. Standard is 10 to 12oz. My parents would have been and still are appalled by such large portions of meat.
My mum never used any packet or prepared foods, other than instant whip. Why she made an exception for that I can't imagine as it is disgusting.
Curries were a regular meal, but they were made with chicken, apple, sultanas, and spices. Odd, but actually quite nice. I prefer that to the tomato and coconut based sauces that are common now.
1970s food was ok, basic but nicer than people make out.