There are a lot of books, too. More than one could read in a lifetime, even if new ones stopped being released. Thus it doesn’t follow that quantity is the problem, or that if it is you’ll eventually be bored by books too.
Years ago I started consuming dozens of books a year. I eventually realised most non-fiction are stretched-out pamphlets: one core idea which could fit into a blog post padded with anecdotes until it reaches book length. The overwhelming majority of productivity books—including the ones typically favoured by HN—fall into this category. A better use of time is to look for an online talk the author has given; you’ll get all the book’s important information faster without the fluff.
Books get boring too. Until you start to develop an eye for quickly identifying the duds so you can abandon them early (or not get them at all). When in doubt, the 2-star GoodReads reviews will typically spell out if a book suffers from too much fluff.
All this to say I don’t think it’s a “books VS blog posts” matter, there’s a ton of garbage in both mediums. Perhaps you’ve just read fewer books than blog posts. If you’re happier with books now, enjoy it.
(I’ve excluded fiction from the conversation because I imagine you’re not talking about blog posts with short stories.)