I've recently made some fairly major changes to my cooking. I wasn't at all interested in cooking; done it for years out of necessity. As you point out, I had to ask myself exactly what it was I was doing with my time that was so important that I ate a rather boring and not particulalry healthy given my food knowledge diet, rather than spend some time in making something wholesome and appetizing. My diet has suffered horribly since I left Spain.The skills can be learned. They really aren't difficult for basic cooking.
Don't nearly all of us have more time for preparing food than nearly anyone else in history? Among other things, most of us don't have to gather the fuel or build the fires to cook over.
Whether or not we have more time for prepping food than people who did it or are doing it, are you really sure most of us don't have time for it?
My family, for example. It takes seven minutes to cook steel cut oats, less if we were willing to eat quick oats but steel cut is more minimally processed with the advantages of that (lower glycemic index, etc). And while the water is heating, I can fill a jar with leftovers or prep sandwich filling. Then, while the oats are cooking, I finish putting the sandwiches together or add the makings of a salad. Add 30 seconds to put the oats in jars and add fruit and another minute to wash up -that is breakfast and lunch in less than ten minutes. Often, the same ten minutes can prep both meals for two or more days for two people. When we were seven, it took a little longer to make all the sandwiches and I didn't try to make more than one day's worth of oatmeal.
Dinner usually takes from a half hour to two hours. Again, that counts the cooking time where there is often no attention or activity other than staying within the sound of a timer. Add ten minutes on subsequent days for reheating and changing it up a bit - such as adding a fresh salad and it yields delicious, wholesome meals for three or four days. We like leftovers.
I don't have any reason to minimize the time I spend making meals. If I did, I'm pretty sure I could spend a lot less time doing it.
If that seems like a lot of time prepping food, we could look at what people are doing with their time instead of cooking. Do so many people really not have time for it? Or is that a convenient way to say they would rather watch tv, play on the internet, etc, etc, etc...
The hard sell is, cooking decent food requires decent ingredients and as I've founf much to my horror; tools! It's quite expensive starting out. I had to buy lots of spices and herbs for example. I found I needed more baking trays, loaf and cake tins, etc.
It's a difficult sell when one can pick up a ready meal for £3.00 that just needs 6 minutes in a microwave. Or, failing that a takeaway meal for around £5.00.