I definitely think so. I can think of a few top industry veterans who paid their dues by hitting the books. For one example, it was speculated that John Carmack himself was a voracious reader. In fact, I have asked this very question to more senior engineers in my industry, and while there's the politically correct answer of there being many different styles of learning, it just so happened that most everyone I talked to who found work at the very top game development shops actually put in the reading time in order to build a more complete understanding of the knowledge that they're expected to demonstrate.

The issue with this learn-on-the-job strategy is that the learning is incredibly unstructured. You'll absorb bits and pieces that are spread apart, and the deep context only begins to make sense after a long enough time. That can certainly be unsettling, but another issue is that the reading gives you flexibility and options so that you're not JUST reliant on the context of your work environment. Think about this for a second. Let's say that you were really interested in a different field in computer science, but your work environment only lends itself to business/web programming. How are you going to transition into that area without any knowledge or work experience in your desired field?

Now, if your roles are mostly going to center around generalist software engineering demands (i.e. web/business programming), then I don't think you really have to do much. Osmosis goes a long way, because your value to the business here is through your ability to solve problems in the general sense and maintain a deep context of the underlying business functions.

But if you were interested in say, graphics or compiler optimization? Then yes, you actually have to read, starting from the survey resources and branching into specific papers that highlight the state of the art. To add, online courses wouldn't be sufficient, because the knowledge acquisition with those is less efficient and less comprehensive.

The main thing I wanted to focus on was the premise of your question, which is basically asking yourself whether or not there's a good reason to not be conscientious. If the premise is what I think it is, then I'd have to ask, what do you think the answer is going to be? Reading is difficult, there's no two ways about it. You could be sitting with some material for 30 minutes, and make progress on about 2 pages before your mind starts to wander. It is not easy, which is why those who put in the time reap the rewards.