I had a similar mindset to you, had bookmarked tens of self improvement books for the areas in life I struggled with, also books for entrepreneurship etc. But I assumed most of what they contain would surface in online conversations etc.
I hate wasting time, so last year I gave audio books a try. I don't like doing chores or commutes not because I don't physically like doing them but because the time it takes to do them - it feels like waste. So I thought "why not listen to audio books while doing them to take the edge off?"
So I started listening to the books I wanted to read while doing the dishes etc. I think last year I've listened to more books than I have ever read in my entire life prior.
I can confidently say that books, if you choose them correctly, are worth it. The curation of content and the layers of depth built into the content (afforded to the author because of the long format of books) gives you a very different experience.
Yes, you can find bits and pieces of wisdom from them online, you'll bump into some of the stuff that is in there. But this idea clashes with your (and my) "efficiency" argument. It would take you years to bump into all the wisdom found in some important books randomly while browsing online. By just listening to them while you are otherwise wasting your time with mundane daily tasks you can be orders of magnitude more efficient with acquiring that info.