This recent Slashdot headline noted there was some recent downtime at Slackware.com, .. Slackware, like a lot of free software / open source coding projects, relies a lot on unpaid volunteers. What is unique about Slackware is that it is very much the vision of one man, Patrick Volkerding. He coordinates every new release with a small team of developers worldwide, including Robby Workman and Eric Hamleers. Workman, I believe, does a lot of work on the website, Slackbuilds.org, while Hamleers is a long time developer who is the person most responsible for porting the Slackware to 64-bit Intel processors, and now is working on an important port to the ARM architecture. That will be very important going forward as cellular sized devices continue to displace the personal PC as the platform of choice. The Raspberry Pi devices could change the world! Slackware, as the oldest Linux distribution still being actively maintained and used, is going to be a part of that. As far as lags in development, from my own experience, most of the recent snags have been due to component pieces of the gnu/linux platform being deficient, notably pieces of X and the kernel itself. The shift towards different graphical paradigms caused some disruption, too. Look to those issues before blaming Patrick Volkerding.
Oh, one other thing, allow me to point out one fact about Slackware's perceived lack of popularity. Why does it appear to shine less brightly than the newer, and perceived rising stars of the Linux world? Well, for one thing, it does have a learning curve. That means it can be off-putting to some. However, once it is mastered, it provides the basis for a lean, mean, fighting machine! It is deployed in quantity by people in the know. For example, at some of the linux conferences I have attended, a few devout followers from certain industries, governments, etc. where stability is a primary asset have stated it is their primary go-to tool. And for what it's worth, those agencies may not desire to have their deployments counted.