I learned to cook in the '90s and '00s, so before cooking videos. I was mostly self-taught, from cookbooks and magazines. I absolutely would have benefited from some of the basic techniques type videos available now: the kinds that show what simmering looks and sounds like compared to what boiling looks like. The kind that shows how to soften onions until they're glassy, and how to sauté garlic without burning it.
My main mistakes back then were simply using too high a heat (though on rare occasion not high enough, like when pan-searing fish), cooking too long, and not using enough oil. All of these things could have been corrected with basic technique videos.
On a somewhat related note, a long time ago I learned how to make gnocchi from an elderly Italian woman. Her teaching technique was immersive: she simply made a batch of it with me standing at her side. There's an art to how quickly you knead the flour into the potatoes: if you don't knead it in rapidly enough you work it too much and it gets tough. You also don't want to overshoot and knead too much flour in. She would work a certain amount in, then have me poke the dough to feel it, and she'd comment on the consistency and where in the process we were; things like "this is what it feels like when you're almost there" and "now it is ready". These things were remarkably hard to put into words, it was a much more immediate thing, like she could detect and point out to me how different it felt from thirty seconds ago. These were things like resilience, just how resistant the dough was to being poked and how quickly it popped back. I can't see how this kind of thing could be conveyed in text or a video, or any way other than in person.