A lot, most if I remember correctly, of the criticism revolved around Lebron joining Dwayne Wade and to a lesser extent, Chris Bosh. Hence Meme's like this
The idea that previous great players would take a back seat to each other, as opposed to competing against each other, was something many just couldn't fathom. Fault the Patrick Ewing's, Charles Barkley's and Karl Malone's of the world all you want for not winning championships, but in their prime, they did not decide, hey, let's team up to beat Jordan. And I can only speak for myself, but that was the most disappointing part of Lebron joining the Heat, was his refusal to compete. This year, more than any other year, he had to compete to win and while winning for Cleveland made this sweet, over coming a better team, is what should make this season one to remember.
But at least with the Heat, prior to landing Lebron in 2010, Miami was not in the playoffs. Yes Wade won a championship in 2006, but Wade and Haslem were the only hold overs. The 2011 team that went to finals looked nothing like the 2006 team, and the 2012+2013 teams were even more different.
Durant took what Lebron did, and completely ran with it to an extent that we'll likely never see again, for the simple fact that we likely will never see a 73 win team again (maybe this year they repeat that total, not sure). This exact same Golden State team won 67 games and a championship in 2015, then as an encore they win 73 games and come within 4 points of going back to back. Not sure how he does not get the same criticism. Yes, he may not be the best player in the world, but what, he's the 3rd? If he wasn't 3rd, he's 4th, depending on how you rank his former team mate, Russell Westbrook.