I totally agree with the basis of your point, but it's a tough one to solve isn't it. If we'd signed Conor Coady (just as an example) instead of Mina people wouldn't have been happy. He appears to be a good captain for Wolves, and has captained youth teams etc throughout his career, but would he have been a good enough player to justify signing for his captaincy skills? And would those skills have been transferrable to us, bearing in mind that everyone who's ever managed Phil Jagielka thinks he's captaincy material but many of our fans would swear that he's not?
I've said before, much of what people call 'leadership' in football is actually just quality. John Terry is, by all accounts, not a particularly nice bloke and therefore not hugely respected as a person, but his undoubted quality as a player maybe inspired his teammates. Everyone was convinced that Coleman was the answer for us but now say he's not. Is that because he's not got the leadership skills or just because his quality level has dropped? To me the solution you're talking about - and again, I agree with you - is signing a real top quality player who becomes our talisman and captain. Unfortunately that's easier said than done.