I think you're flogging a dead horse if you're trying to paint him as a mercenary or being disloyal.
Yeah they didn't win anything in 13/14 I believe but he stayed.
Years ago players often played for the same club man and boy until they retired or at least only played for a handful of clubs however with big money and transfers that's all changed so Messi being there for so long is unusual
OK so Messi has been paid handsomely for his time at Barca however he has been loyal and look at the titles and trophies he's helped them win along with attracting other top players to the club
Barca have a major rebuilding program that is needed and with a new Manager who is tipped to be replaced before the end of the season it doesn't exactly inspire confidence, perhaps if Pep was going back there he would stay but Koeman
He hasn't got many seasons left at the top level so why not move on, i've been surprised he hasn't come to the prem before