My mother couldn't cook - she did cook everyday, a lot, but the results were
She baked her own bread everyday, the loaves were like house bricks they never rose above the top of the tin and came out with an impenetrable crust and the inside of the loaf was dense and chewy.
Main meals were bizarre concoctions that involved meat and veg that had been put on to cook at the same time with the exception of frozen peas, they were placed in a sieve under a running hot tap. She kept a big earthenware pot next to the cooker where the fat & juices from everything were put, the resulting grey sludge was then used in everything from pastry to gravy, it was so disgusting that even the flies avoided it. When I started school and tasted my first school dinner I thought I was in heaven, I never knew food could taste so good!!!!!
She is also the only person I know who would regularly buy a new cooker because the current one was so filthy it stopped working or would catch fire due to all the oil, fat and gunk on it. I don't know why nobody told her how awful her food was, she was in her seventies when one of my DC's said "I don't want dinner, your food is horrible" there was an awkward silence and he just looked at me and said "well it is" he was only four but it ruined Christmas Day.
Growing up we were three very skinny kids with the fattest dog and cats on the street. I became a vegetarian at twelve and happily lived on salad and cheese.
In general I agree with you OP, even my mother could have improved. I think some people avoid cooking because convenience food is just too easy and schools stopped teaching the basics, my kids did food technology but it was hardly cooking - a salad, all prepped at home, a pizza base topped with passata & cheese, pasta & pesto etc. One did GCSE and did afternoon tea as her project but was encouraged to use packet mix cakes and bought bread - hardly cooking, I was really shocked, she did loads of theory a nice folder full of recipes she never actually cooked at school and nutritional information.
When I was at secondary school we started with the basics, ten ways to cook eggs, potatoes, soup etc and moved on to cakes pastry and proper meals. It gave me a good understanding of "how to" and the confidence to cook.
I have a nine month old grandson with a mum who can't/won't cook, it's easier to order a takeaway, give her son food from a jar. Her argument is that her kitchen stays clean and she doesn't waste her time. I despair.