Were Mata and Matic leading when we were struggling with Jose? Did they just decide to stop leading when LVG got sacked? Then Ole gets hired and they decide to start leading again?
And regarding Arsenal -- I can't tell you if you're wrong or not about their "culture" (another very fuzzy concept....) but I can tell you that you have no idea! You aren't at training, or in the dressing room! And are you saying that the only reason that our season progressed after losing to Arsenal and their season tanked is due to "leadership"? Nothing else played any part of it? I'm skeptical mate.
United suffered the big year 3 implosion under Jose. The setup under Jose was never going to work unless he got what he wanted. Yet he won silverware Year 1, and finished 2nd Year 2. Mata and Matic are still here because they lead and they are model professionals that all football players have respect for. Just because your team isn't successful as a group doesn't mean you have a lack of leaders. As we can attest with Arsenal, the leadership pales equally with their talent.
Ashley Young and Valencia stayed so much longer at United because they were leaders and professionals, through thick and thin. They also were club captains and captained the side many times. Similar to Matic and Mata, who have captained the playing side.
Arsenal have nice, young talent. But no real shepherds to guide them and groom them, to take the heat off them, to protect them. A manager can only do so much protecting, because players have to have that protectorship and accountability within their own ranks. Auba and Lacazette are good players, but even with the two of them on the park together, they haven't been able to get it done over the course of a campaign. Martinelli is young, but is he really going to overtake Auba or Lacazette? Only by merit. Pepe is the club transfer record, yet cedes his place to younger players, and rightfully so. Who is going to help Arteta manage him and get him in the right frame of mind?
There's a nice core of young players Arsenal have, but they too need to continue to keep improving a lot and mature at a fast rate if they want to finish Top 6, which would be a great accomplishment for them.