Why was everyone so upset about URF? They told us it would not be back on the first of April.

Well 2 Probelms:

1. People still wanted Urf, yeah ofc Riot said they wont release it - still people hoped to get it just as last year*. And this hope was destroyed.
2. Draven Day, was kinda... meh.. a mediocre fun-merch Event with forced on features some people considered annoying - that's nothing anyone will keep in good memory, unlike other April Fools Riot created - The legendary Lee Sin Champion Spotlight, Urf, Chogath eats the World/NyanTeemo and OFC Ultra Rapid Fire!

This combination made some people pretty angry - to be honest, it's the Internet a decent shitstorm was not really surprising. x'D Dont get me wrong, even a great URF-Replacement would still have caused a small 'Give us URF'-Wave. ^^

*This is another mistake Riot made. They said 'No-Urf' once before and still brought Urf back. Non of the URF Fans actually believed in this statement.