Books are useful for a couple of reasons.

1) It can do wonders for focus to disable your network connection, open a book, and work through examples (but maybe I just get distracted easily). This actually applies for most tasks that involve a computer and don't need the internet.

2) Not specific to print, but a book that covers a topic in a structured, beginning-to-end way can help reduce gaps in one's knowledge. I learned a bit of BASH by just googling around and reading Stack Overflow, but reading The Linux Command Line (https://www.nostarch.com/tlcl) taught me things I wouldn't have gotten in 10 years of stack overflow browsing.

Online resources are often shallow in content. I prefer to deep dive into a topic and truly learn it inside and out by reading a good book. Blogs and tutorials don't give you that deep insight.

Do you read enough books to have an informed opinion on that?

For me, the best way to absorb knowledge is text. Video makes it much harder to skip parts (you can jump forwards but you can't quickly skim to make sure you have a vague idea what you're skipping. You can speed up and slow down videos but it's far, far more clunky to me than varying between skim reading vs deep reading. I've spend literally decades now doing that every day when you think about it, varying digestion speed by orders of magnitude without thinking about it, no chipmonk voice involved.

Hyperlinked text might be better, so that you have a graph of knowledge not a searchable seq(book with chapters and an index), but there's a natural order to learning things, the teacher hopefully has an idea what order it makes sense to put the concepts in front of you in.

tldr; books are hard to beat, if something was going to beat it for me it would be a well designed, portable wiki of the book's contents, maybe with some interactive exercises. Definitely not the video lectures and homework of most online courses.

A book can be coherent and curated in a way that a collection of posts by different authors cannot be.

Many people prefer books to screen reading. Many people also learn better from reading.

There's only so much you can put in a blog or lecture series. Most college courses don't even cover a whole book (in STEM subjects).

Software design is relatively timeless. Your not learning technologies, your learning how build software in general.