Books changed the way we think about thinking.
The printing press changed the way we think. Knowledge was no longer restricted to just experts, it could be spread to anyone. And just like Isaac Newton, we could all now stand on the shoulders of the knowledge gained from others.
It was possible to think more creatively because we could now break down the silos of different minds and come up with new insights nobody could have come up with alone.
I'm going to specifically talk about non-fiction as "books" here, but many of the similar points apply to fiction too.
The internet has made knowledge far more accessible than before 👍🏽
The internet has changed the world of knowledge completely. Imagine a time before you could look up the answers to your questions at the click of a button on Wikipedia or Google!
More than that, access to information is now 24/7. To answer that niche trivia question you no longer need to be dedicated enough to go to a library, scour through book after book until you find something you're looking for.
Research was made easier, you no longer needed to dig through every journal to be on top of the recent developments in the field. You can find the latest, up-to-date papers just with a few keystrokes. Literature reviews become much less labourious.
The internet has AN answer for everything? 👎🏽
The problem with the internet is that it only has ONE answer for everything, or far too many to be able to sort out the garbage.
Wikipedia will have an article, but it is one person's understanding. This is systemic and intentional; you cannot create a secondary article on any topic that exists. And most editors are not willing to let an existing page get a complete re-write unless it's factually incorrect.
You can get many different books about a certain topic. If you read one and you don't quite understand what they're on about, you can just find another one and try your luck again.
This is why we have lectures, small class supervisions, essay writing at University. The more ways we are exposed to some information the more likely it is we'll "get" it.
WebMD is a joke for telling you every little symptom you have is cancer. Wikipedia will have the very specific details of the chemical reactions needed to produce a drug, but no discussion on how it works and how it relates to a big-picture view of human physiology. It is notoriously bad for anything mathematical; everything is explained to the level of a Maths PhD without explaining any of the reasoning that led to it. Just the end result. This robs us of any critical thought or ability to assess the process of how the information came to be.
What's bad on Wikipedia is even worse elsewhere. The internet has a notorious problem with verifying information. If you stray too far from the one or two authorative sites, you'll likely end up in the lands of conspiracy theories and "alternative facts".
Books solve this problem by firstly having a barrier to entry, so that publishers need to decide something is worth it before printing it, and secondly by being possible to use the internet to get reviews on books so that you know you're getting a good one, something that's impossible to do with websites.
Books provide continuity of thought 👍🏽
This is key whenever the piece of information is not a short snippet you are after.
If I want to learn the piano, I could watch YouTube videos all day long, but each video is a short snippet of the process of learning. After I've done that one, I don't know enough to be able to find the one that is slightly harder that I can still do. They aren't ordered to make it easy for me to learn.
On the internet, there's just a web of loosely related information, algorithmically generated to maximise my viewing time.
A book will have a series of exercises that have been carefully thought out to maximise learning. It will have a structure that goes in order of difficulty, and the confidence that it has worked successfully for many people. You can't say that about a wikipedia entry.
Continuity of thought is important because it lets us logically reason with the information we are given. Just an answer doesn't do that. The process is more important than the destination. The internet only has the destination.
The internet is good for superficial knowledge about lots of topics, books are good for in-depth knowledge about a single topic
Books have evolved through literally hundreds of years of evolution to distill topics into a format that is easy to learn from. The first few decades of the printing press probably weren't very good compared to now. The internet will probably improve as we find new ways of addressing these issues.
But for now, I think books are still the best way to learn about a new topic in-depth, while the internet is a good way to learn about lots of topics superficially. If you want to learn about something new, or a new skill, the best way I think is to find the best book about it online, and then go read the book instead.