Ahhh - golden age of internet fun. Looks like they sold the domain and/or pivoted a bit. Feel like a modern version would be relatively easy to monetize if someone were to ramp it up again.
I've noticed https://clicktheredbutton.com quite a lot in my referrer analytics. I don't know if it's as featureful as StumbleUpon was (I never used it) but it seems to have some fun sites