
You can blame that fukkboy Dan Gilbert for this entire situation happening ("The Decision", the formation of the Big 3, the Heat dominating), and here are the reasons...
1. He failed to put in place a great front office that could have given

proper help that would have led to them winning championships and Bron not leaving Cleveland.
2. He was the main owner whining about CP3 going to the Lakers, which led to "Basketball reasons". Maybe if he had not cock-blocked the trade, the Lakers could have been the team to take out the Heat. (knowing how Gilbert is, he probably felt that a depleted Cavs team would be the one to stop Miami)
So for everyone being upset at the Heat for forming the Big 3, dominating the league, and potentially getting a top player such as Melo, this can all be traced back to Gilbert and his fukkery. So if there is anyone to be mad at, it is him.