History of KiSS
Over the decade or so when KiSS was actively used, different groups of people used KiSS in different ways. I'm basing the dates below on OtakuWorld's "time" listing and vague memory, since I wasn't around for most of it. Would appreciate clarification from long-time participants in the community.
Most dolls were based on anime/manga characters. Lots of pornographic dolls. I get the impression that most of the folks making these dolls were 4chan-before-4chan.
An early Sailor Moon doll by MIO.
Most dolls are still based on anime, but now non-Japanese artists are making them. Not as many Japanese artists are submitting to Otakuworld. The non-Japanese anime fans are also making original character and comic book-inspired dolls. Still lots of porn.
Male and Female Ranma by Dov Sherman
I feel like there was an "era" here, when KiSS wasn't all about anime and it wasn't all about cute fashion either. Maybe call it the "era of Emby Quinn". :)
Emby Quinn self portrait
This is the era I'm most familiar with. Kimiki, Silent Angel, Punky, and RyogasGirl all started making dolls in 1999-2000. All four were teenage girls and anime fans and together they started the trend of cute fashion dolls that took over the community at its peak popularity. Their dolls were mostly very kid-friendly and attracted a lot of younger people to KiSS.
By 2008, the KiSS dolls forums were dead, the few artists left had moved to deviantART, and only a few dolls were being uploaded to the Big KiSS Page each month. The Big KiSS Page was last updated in 2012. So what killed KiSS?
The most important factory (IMHO) is that tools and viewers and the tutorials dependent on them became out of date. In the mid 2000's, artists who upgraded their operating systems started finding that their KiSS-making tools were broken. The work-arounds and alternatives were so frustrating they'd often quit making dolls altogether. Aspiring new artists had to figure out which tutorials were accurate and which were outdated, so usually they quit and went to other technologies like IMVU or Flash. Today very few tools work with Windows 8, except for UltraKiSS. And while UltraKiSS works, the creator for some reason found the need to cover the app in obnoxious fanservice-y anime art, so some artists (including myself) refuse to use it.
The KiSS community was also far too dependent on a single site, OtakuWorld, and a single developer, Dov. Dov did incredible work, but KiSS artists should've taken more onto themselves in terms of hosting dolls and creating tools. When Dov had a personal crisis for a year or so and couldn't update the Big KiSS Page, it was pretty much the death knell for the community.
Another issue was the blend of kid-friendly, teen-friendly, adult, and pornographic dolls that were available. It was hard to tell if a doll was going to be a cute mix-and-match fashion doll or something very very creepy. At the time, I just winced and deleted the file if I guessed wrong, but as an adult, the prospect of accidentally downloading child pornography is a lot more alarming. I imagine many younger users were prevented from enjoying KiSS because of stuff like this.