It doesn't look like there has been activity since 2016. Whats up?

Nope, they were replaced with the Scenario Hall in the RPG Centre.

We don't get White Scenario XP rates, though. Or even close to it. 500 max in total per scenario, where with a WS, you could get around 75-100 on average per decent post.

But yeah. White Scenarios basically died down as playerbase and GM numbers went down, so they were discontinued.