The core of Diablo is just to kill monsters over and over again, collect items and level up so you can simply repeat it all over again.
The core of angry birds is to fling your birds at stuff over and over again in slightly different ways.
The core of Counterstrike is just to pew-pew at other players over and over again.
And yet, each is (or was) a seriously addictive game that is/was very popular.
Most games at their core are fairly basic and repetitive.
At least with ED you are not fixed into doing a single type of task repetitively. You are free to chop and change as much as you like, and when that gets a little tiring, you can always go and do some pew-pew in CQC if that is your thing.
Wow.. you are comparing ED to Angry Birds? Thats very very sad. That is something a kid will play on their phone or ipod while waiting in a Dr's appointment or something like that. You also sort of defeated yourself by even trying to make a comparison. Angry birds has a vast number of different unique challenges. ED has only repetitious challenges with the same outcomes. Angry birds has goals... ED really does not other than to continue to repeat yourself over and over until you raise your dollar figure or your rep a percentage. Angry birds came up with a good fun formula that had infinite variety. ED has the core in place but not the infinite variety yet. I mean its there but there is no way to interact with it.
Diablo was indeed popular and it was fun for its day for a while but then it got old and boring once you learned all you could possibly do. BUT it also had an infinite variety of loot and all sorts of other randomly generated stuff. It was fun to explore the dungeons and it had a good story. ED doesn't have that nor does it have anything that engages you. It was a boring clickfest for sure once you cleared it, why bother after that for sure. But it was fun when you went through it.
Counterstrike is a competitive "sporting" event. That is apples and oranges. That is why they tried to make that arena in this game nobody plays. There is a trend going toward online sporting games like rocket league, dota etc. Apples and oranges.
Literally your argument has failed. I get where you are trying to come from though. You CAN make repetition FUN for sure if you do it right. ED has not.