Honestly it's all down to coaching style. Ever since Pep left, we have coaches that cater more to individuals than the team.
Back in 08-12, Messi was a self-sacrificing part of a larger unit. He may have been the best part, but still a cog supporting the machine. Ever since Tito and now Tata, we play as a group of individuals and he's simply "the boss". Not the leader, not the captain, just the alpha-wolf who calls the shots on his own actions. Even if the individual route brings him success, he'll be served instead of doing the serving. We're not getting the most out of Messi this way.
It's not his own supposed "bad attitude" that is causing this, it's a lack of tactical discipline within the team. Any player will always be satisfied with themselves if they make as big an impact as Messi has, so you can't blame him for thinking he's done his part. What players fail to differentiate is that while they do play well football-wise (good individual actions, doing what they do best, getting goals/assists) they don't devote their fair share of tactical/team work (pressing or at least covering zones, having good movement and involvement in TEAM-play rather than their own plays). There are actions a player does that support their own plays and individual performance, and there are those that support the team and help lift the load.
This does NOT point towards a lack of character in Messi. It's just that when a person becomes great to that level, they feel that their individual actions are all they are responsible for as their contribution to the team. On some level, that is the main contribution because the team does rely on Messi's goals and assists. However, Messi will drift farther from being a group player and closer to an individualist until a coach (new one as Tata isn't the type) reboots the entire system and makes every player a cog in the machine again, with every action serving a greater purpose.
With the fall of the machine that is Barcelona, players are becoming more and more individuals who decide for themselves what they feel like doing. It's not as cynical or immoral as it sounds, honestly it's a natural progression even if a very negative one. Alves, Pique, Messi have all went this way on some level.
