Both approaches are not incompatible. It's probably more efficient to build a high level map of the subject using podcasts/YouTube videos than reading a dense book. Once you have that high level map, you have the tools to choose the dense book that is more appropriate for what you are looking for. That way the number of dense books that you have to read is reduced compared to a world without YouTube/podcasts, and the end result is the same.

Of course, if you stop just after the podcasts/YouTube, you end up with a biased map of a subject which ends up probably not being very useful if you want to apply that knowledge successfully.

Most schools will only ask for the first part, so that is enough for the kids. But I mean, they were already doing similar things beforehand to avoid having to study dense books...