I would recommends the Youtube rabbit hole of Neil Postman lectures from the early 1990's that outlines this very observation. ( I don't expect you to subscribe to all his opinions, but he does attempt to analyze the impact of different media)

I won't go as far as to say reading is the only medium for self-development but I will challenge you, dear reader, to take a photo of a page of a book, then a photo of any modern website and compare the design elements. Books are less distracting, and are not designed to steal your personal agency with the strength super computers.

Books allow for greater introspective focus on complex ideas. In fact, some concepts worth learning require several hundred words to describe. Practicing the ability to singularly focus on long form thought is a great skill to have. It is a form of deep work/thinking.