I don’t think Slackware was ever widely used

It is still supported and used. It’s been my distro of choice for several years.

if you choose the current or the stable stream, last update was yesterday:

• http://www.slackware.com/changelog/stable.php?cpu=x86_64
• http://www.slackware.com/changelog/current.php?cpu=x86_64

If you need help, there are many users that can help you here https://www.linuxquestions.org/questions/slackware-14/

Is the package manager still too dumb to figure out dependencies automatically?

I still use Slackware and it’s a great distro. I very much enjoy its batteries-included approach (a full install comes with pretty much everything pre-installed) and I enjoy its simplicity and ease of configuration and use. There’s a learning curve to get there, but once you understand how everything works it’s a distro that gets completely out of your way. The bonus is that if you understand Slackware, generally, your knowledge of GNU/Linux broadly will mean you’re never lost on any other distro either. Most of my frustrations with other distros actually stem from them patching something/doing something weird with config defaults, whereas Slackware ships stuff as it is from vendors with vendor defaults which I find a lot more palatable and predictable.

Philosophically, I like how Slackware is independent and beholden to no corporate entity. Controversies that have hit other distros in the past as a result of that just aren’t a thing with Slackware.

Slackware is a very rewarding distro to use even in 2023. It’s not for everyone, but I imagine there’s a fair amount of people like me who’ve probably been using it for ages and have had absolutely no reason to ever consider using anything else. Once you’ve got everything you want and configured stuff to your liking, it’ll just work forever fantastically.

Removed by mod

Slackware may not be huge, but it is the base distro for Unraid.