DM taught us all (6 DCs) the basics - 3 did hotel management in college so learned a lot more as part of that, but all of us CAN cook decently (not all WANT to though...
). In my own house, it is a mix of convenience when life is hectic, and from scratch when we have time. So I have jars of sauces, packets of frozen veg, fish fingers etc, but also lots of spices (both individual and in mixes) and basic ingredients like different types of beans, all sorts of pasta/polenta/rices/etc, baking ingredients etc.
DH is also the eldest of his family (like me) so also had to cook at times (his DM was quite ill when he was aged 10-15ish and his DF couldn't cook at all!) - he was a more basic cook leaving home because that's all the family would tolerate but really enjoyed experimenting when he left home. So while he doesn't tend to cook as much now due to less time than me, he is a good cook from basic ingredients too. And we have a well-thumbed shelf of cookery books for experimenting with still.
DH's siblings though are far less competent in the kitchen. His DB doesn't cook (when he worked away from home, he depended on DMIL giving him 4 plates of dinner every weekend for the 4 nights he would be away during the week...and it's not much better now he has his own family). He is a "heat things up 'til they're hot" type of cook.
DSIL is better, but more of a heat things up person or very basic cook (fry/grill meat, boil carbs, boil veg, serve). But her family are very plain eaters anyway. And I know that most of my DSiblings' OH's are similar - heat things up cooks IF they cook, a couple WON'T cook. (But there is 1 who is another great cook - that is another big foodie household).
In our house, our DD is the problem - she is also a good cook when she wants to be, but has recently decided that everything needs to be "blow your head off" levels of spice and heat - which I can't manage (I can manage some heat - but say M&S 2-3 chillis level, not 5!!). But she will also find recipes online, so has learned how to bake dinner rolls (yeast bread) over 2020 to quite good results, makes a really nice turkey chilli when she reigns in the spice or puts out plenty of crème fraiche, and will regularly cook her own meals.
But while we have had both a lovely steak dinner and duck breast (1 with mash, the other roast potatoes, and various different veggies) dinners over the weekend, we also had an M&S ready meal. And DH loves a fish finger sandwich for lunch on occasion.
Sometimes dinners are a bit random - I do a lot of stirfries to use up handfuls of veg, but do try and put things that will work together. I do add extra veg to sauces like spag bol, or shepherd's pie - but mediteranean type veg (peppers, courgettes, etc) to Italian sauces, but more earthy things like carrots and peas for a shepherd's pie, so not totally random.