I'm in my early 20's, grew up watching YouTube, and still find textual documents superior for learning in almost all cases (with the exceptions being concise and intrinsically-animated things, like a lot of 3b1b's videos).

I don't think that there's nearly as much adaptation as there is just people getting used to watching video content and liking it more. That is, greater enjoyment, but not greater comprehension.

I suspect that nearly everyone who thinks that they "learn better from videos" just enjoys the videos more (which affects how well they perceive their own learning efficiency - humans are notoriously bad at self-assessment especially in the cognitive realm) and/or has attention issues that are mitigated by the more engaging nature of a video.