For me spoofers are main culprits. If you don't want to play the game as it is supposed to be then choose a different one couch potatoes!
Hackers! Well yes! Who wants your account hacked, if it happens to be your Google a/c then many other things too. So, lets keep it to games prospective.
The Ex system, I care a damn about it. Not doing raids, no fun. Can't see anyone playing, if I can see them on Radar just like mons. I could ask them to join me for a raid.
No fresh content! For sure! Too little Too late! Why fix something which is working already? Well! it was broken in very first place.
Lack of communication! Not really, just received a couple of notifications offline, about my mons getting knocked out of gyms and a congratulation message saying I am now more than half way thru to level 40. I had my 7th day streak coupled with egg hatching 10K eggs and evolution spree(Thanx to xtra candies during the event) coupled with a couple of lucky eggs. I wish they congratulate me when I reach 10,000 KMs some 20 odd KMs short of it.