The lack of effort was what got to me as well. While I'll admit the Draven heads was funny...for like 1 game but nothing that should of been planned to drag out for like 3 days. Also yes they did say that we wouldn't get URF for April 1st, but other than the fact that they said that last year, they also kept saying April 1st so I (and I'm assuming a lot of other people) were thinking that it was going to come today since it's the 2nd, but guess not.
While yes we will get urf in the rotational game at least 2 times this year, but with each time only being like 2-3 days each, that would be only like 5 days this year. Also with the rotational modes only happening on the weekends, what about the people who are generally busy on the weekends and only actually have time to play during the week days? Do they just miss out on urf and every other game mode because Riot decided to only have each game mode show up for 2 days a week, instead of the whole week?
Some people were actually really looking forward to urf and I saw some people even said that they took a day or 2 off of work just to play it. What about the people that took a break from league and was planning on jumping on just for urf? Since we didn't get it, they'll probably just log off and wait for it to show up in the rotational que which other than the fact we don't know when or how long that'll be, but we don't even know how much of a heads up we'll get before hand.
Another reason people were also mad was because of the lack of responses or anything. No one from Riot made a post, or responded to other post and just feels like they're trying to ignore everyone. Even if it's something small like making a post on April 1st to tell or remind everyone that we won't get urf or whatever, they just kept quiet and let the community rage at each other for 2 days.
People are angry because the event felt like it could of been way better.