I remember back when reddit was supposed to be the "new slashdot."
Are you sure it was Reddit they were talking about? From what I remember- and commented on in this post from 2008 (i.e. when this was still recent history)- it was Digg that was getting all the hype and being spoken of as- essentially- an improved, next-generation Slashdot.
Digg's disastrous and rapid decline into near complete irrelevance several years back (#) have pushed it off the radar to such an extent it's easy to forget it existed at all, let alone the fact that it enjoyed several years of major popularity and had been a poster boy for "Web 2.0" in its early days.
Having checked its Wikipedia article, Reddit has been around almost as long as Digg (mid-2005 vs. late-2004). That doesn't surprise me that much- if I think about it, it's a site I'd been vaguely aware of for quite a long time. But it definitely seems that its current level of prominence is only something that's been attained in the past few years (i.e. post-Digg)- which would tie in with what I'd heard, that a lot of former Digg users moved to Reddit.
Anyway, this isn't a defence of Digg, just an attempt to ensure it's not inadvertently written out of history- for good or for bad.
As my linked post above makes clear, even in its early days I grew quickly disillusioned and watched it go downhill before my very eyes. And in hindsight, Digg- or its users- were some of the first to really highlight what would become many of the negative aspects of social media unleashed on the public at large that we know today. Such as the (then-hyped) "wisdom of crowds" descending into mob mentality, attention grabbing stories, manipulation and suppression, etc.
Digg arrived around the time the Internet was moving away from being seen as something for geeks and esoteric types, even past its late-90s/early-00s "cool kids" fad-dom and was becoming something that pretty much everyone used. If it was ever meant to be something akin to "Slashdot on steroids"- and I'm not sure that it was- it quickly way beyond that into a much larger and more general-interest audience with discussions and submissions covering much wider fields of interest; basically a forerunner of where Reddit is today. By the time it over-confidently misjudged its footing and went careering over the cliff edge, Digg was- AFAICT- far, far larger than Slashdot had ever been.
It's possible that when it originally launched in 2005 that Reddit might have been compared to Slashdot- or equally possible that you're back-projecting its latter success onto what people said about Digg! However, by the time Reddit (essentially) took over from Digg a few years back, both had gone far enough beyond Slashdot in terms of scale and audience that it didn't make sense to compare them.
That's not a criticism of Slashdot; it's a specialist, geek-oriented site, and always was. That was just less obvious in the days when most people on the Internet *were* geek types. I don't know what its traffic's like these days, but if it seems less prominent than it used to be, that's as likely because what was once a fairly tall building in the days when the Internet was geeky remains the same size, but is now dwarfed by skyscrapers surrounding it, i.e. sites used by the type of people (i.e. the vast majority of the public) who weren't on the Internet 20 years ago!
(#) Apparently precipitated by a major and disastrous redesign circa 2010, on top of growing competition from other sites and social media