I used to play the original Natural Selection years back, but I never really considered the sequel. I'm not sure why, but perhaps it involved the price-tag (being skint at the time meant I couldn't buy it).
I used to play hours-on-hours of NS 1, alongside the original Zombie Panic!
Playing as a skulk, ankle/waist-snapping unsuspecting marines and then imploding? Loved it.
The servers that enabled the disabled weapons (such as the spikes for the lerk) and marine versus marine play were fun, too.
Carrying gorges around and placing them on ledges to bile bomb... classic.
As for the modding community/game development community... you can blame Valve for that.
They're not the same company they once were in both spirit and practice, and have become as bad as other reviled major developers.
To use a meme: "they dun fucked up."
It's a crying shame: the Gold Source and Source communities used to be one of the strongest around, rivalled by the Unreal Engine's own. But, it's pretty much dead, now.
A real shame.