I think some degree of caution has to be exercised when judging these things from the outside though. Could be that Puig is another Ravel Morrison or Mario Balotelli. Or maybe he's just hideously overrated based on a few individual abilities and doesn't work well in a team setting. Huge talent alone has never carried anyone, and it's probably less likely to impress someone like Koeman who himself was a top player for years.
I've heard for years that Puig is supposed to be the next big thing but Koeman is not the only one who's been reluctant to use him. There seems to be a diskrepancy between how he's rated by the fans and how he's rated by the coaches, and I can't help but feel that it's a bit similar to Giovani Dos Santos and Bojan in the past, or even Sergi Samper. If there's one thing Barca are great at it's pretending that their talents are better than they actually are.