I think Messi--unintentionally and through no fault of his own--crushes the hopes of potential successors through the sheer enormity of his legend (Bojan, Coutinho, to an extent Neymar, etc. etc.). How can anybody live up to / aspire to being / succeed in becoming the next Messi or the successor to Messi at Barcelona? That club is destined to not recover from the loss of Messi for at least a decade after he retires. They made that bed and will have to lie in it. The whole demigod thing with Messi at Barça--the way they literally worship him--has always made me extremely uncomfortable. I hope we never become so dependent on anyone.
I think that's true, and whilst they might well be 'More than a club', they've lost sight of the fact that they also needed to be 'More than a player'.
Messi has defined them for over 10 years, and as others have mentioned - the production line of quality from La Masia has dried up almost completely. The move from the traditional Spanish farmhouse in the shadows of the stadium to a modern glass box was intended to automate the home-grown production line and increase the odds of finding the next world class player. Yet since it's inception in 2011, I can't think of any player of note who has come through, and perhaps the break with tradition from a 300 year-old building that had been in the clubs DNA for decades somehow broke the spell.
The likes of Messi, Xavi, Iniesta, Pique, Valdes, Puyol, and Busquets elevated Barca (and Spain) to world beaters again, and they now look increasingly reliant on either big money signings or astute transfer business. The first approach succeeded with Neymar and Suarez (whilst the other players around them were still in their prime), but failed with the likes of Dembele and Coutinho as those other players began to fade. The jury's still out on Griezmann who has massive boots to fill. The second approach of finding unpolished gems at other clubs and turning them into world beaters - something at the very core of Jurgen's philosophy - hasn't really been seen at Barca for almost a decade now.
What this all means for us is that Barca (along with Real) are no longer the feared greats of Europe and both teams will continue to be in transition over the next 2-3 years, during a time when we're at our peak. Real might well boast a recent hat-trick of Champions League titles, but their focus on being 'the best in Europe' belies their poor showing in La Liga - winning just 4 titles in 15 years in a weak league. For Barca, Messi is so often our Gerrard of old - rescuing the game when it looked dead, and lifting those around him to become better players than they are when he's absent. The aura when he's gone will be impossible to replace and it will be interesting to see how Barca adapt and cope in the years that follow. They may well keep him on in some other role at the club to serve as an inspiration, but he might also haunt the club with a reminder of what they've lost and the gulf in quality that players are trying to bridge. That's one of the reasons I'm glad we didn't keep Gerrard at the club - despite the clamour from some for him to stick around.
Despite their issues with money and politics, I've always admired Barca for their approach to football, the development of youth, their style of play, and the contrast with their biggest rivals. But those days seems to be coming to an end as the likes of Messi, Busquets, Pique and Suarez enter their twilight years. It's time for a new dominant force in Europe and no-one is better placed than us across all of the leagues to be that team.