Come on. You make it sound like all Xavi (or any other manager) had to do was turn up and Barcas fortunes would miraculously change. Why couldn't Koeman get a tune out of them if it was so easy? After all, he was part of the dream team.
First off, I don't make it sound miraculous. There is nothing miraculous about Laporta picking the right man to move Barca forward, supporting and trusting him to do so. This guy did it the first time when he picked Rikjaard and then Pep when Barca was in a bad way each time. I thought that went without saying so I dibt bother mentioning it.
Xavi's success is DIRECTLY because he is the absolute right man for the task at hand: A man to lead with the traditional footballing principles using LA masia more than recruiting as the for for a rebuild. Plus a brave choice by Laporta because it would have been way easier to go for a more established name.
Second, Koeman couldnt get a tune out of the team for two reasons. First, he wasn't implementing Barca's core traditional footballing principles and secondly, the barca hierachy neither respected, believe in nor liked him. Its kinda hard to succeed with both hanging over your head.
The real night and day is Xavi coming into a team of aging players, Busquets, Alba, Pique, Alves with academy players who are 17-18, realising what needed to be done by bringing in Auba, Adama and Ferran and actually gelling it all together which is a hell of a lot harder than what it sounds.
You simply keep missing the point! The old guard and the La Masia lads led by the outsider Pedri are ALL schooled in Barcelona's traditional footballing principles. Gelling that football together was NEVER going be hard. Especially when he was literally their leader and implementor in chief of those things as player himself, not long ago.
I can guarantee if he was taking over a dressing room like United that doesn't have ANY players from one footballing direction, nor an under lying club philosophy from the youth, schooled in the footballing principles he believes in, he'd have objectively found it 3 times as hard to make even a quarter of the progress he has had at Barca.
What has actually taken people by surprise is the excellent recruitment of missing pieces of the squad in the January window that has allowed Xavi's Barca to close the footballing gap between themselves and Real Madrid. Both Xavi and the leadership deserve credit for identifying the right targets (Xavi) and supporting the plans (Laporta and crew).
United has no such synergy and that is a bigger reason why things have consistently failed since Fergie left. Its ultra simplistic to pretend its just the coaches who weren't good enough. That is the true day and night between both clubs.
On the other hand, you said yourself, "A United for example will only improve when the next manager is allowed to make a massive clear out and start his ideas with a clean slate." Didn't Ole have that luxury for 3 years leaving us in no better shape than what it was when Mourinho left?
Let's count the players still from past regimes at the core of the first team in that period:
Degea, Shaw, Bailly, Lindeloff, Fred, Mctominay, Matic, Pogba, Rashford, Lingard, Martial, Mata
All ole added was AWB, telles, Maguire, dvb, James who was exchanged for cr7, Cavani and Bruno Fernandes
First, that wasn't much of a clear out
Second. People need to stop pedaling that lie. Mourinho left behind a broken and utterly disunited dressing room and a club strugglng to maintain a Europa league spot. Ole got the dressing to a better state, re established a link to the youth and first team and the oath way between the two and did not struggle to finish top 4 two seasons running. He was just never good enough to take the club to the next step of challenging, in spite of his several semi finals and trips to a final, so hit a wall and needed to be rightly replaced this time with a proper long term plan. You don't have to rate him as a manager to give him credit where its due. He definitely left United in a better state than he found it. Just not competitive enough.
Defend Ole all you like but I stand by my statement that what Ole has done at United and what Xavi is currently doing at Barca is so obviously different it shouldn't need explaining.
I insist Barcelona and Manchester United are not renotely in the same state for the situations to be comparable. That's something that shouldn't need ANY explaining.
I also know Ole is your favorite punching bag. But it will serve you well to realize everything I stated about the club was the exact same for Jose Mourinho. Anyone who thinks a Xavi would do what he has beeb doing at Barca' in United's current situation yielded by the Woodward era or errors, because of his coaching skill alone, is simply deluded beyond reason, I'm sorry to say.