Great shot stopper, back to his best, having a great season, world class etc
The source of the pizza chart (above) comes from the analysis below. And it's pretty obvious to anyone that understands the positional play principles that De Gea doesn't suit the style of play in question. Luis Enrique who similarly wants to dominate all phases of play and is a Champions league winning coach, had dropped him from the Spain squad. And the reason for that was because he wanted his keeper to initiate the attack in the first phase in possession and be a dominant presence in the box. And De Gea isn't good at either of those disciplines, which are a big part of goalkeeping in today's game.
When Schmeichel left the club at the age of 37, we lost a proactive keeper with a big box presence. So yes, we did lose a great keeper but the way we went about replacing him, was why we couldn't replace him adequately. Bosnich, Barthez, Taibi, Carroll, Howard etc were not going to replace him. But if we had tried signing Van der Sar from Ajax or Francesco Toldo from Fiorentina, then I believe one of those keepers would've replaced Schmeichel. Van der Sar as it turned out would arrive via Fulham, years later.
If we had attempted to get the best keeper to replace Schmeichel, then we would naturally be looking at the likes of VdS, Toldo, Pagliuca etc for that time period, and not the likes of the ones that actually arrived. So with the benefit of hindsight, it's easy to see why we struggled to replace Schmeichel.
It's also not about playing crazy high lines, but rather it's about being a dominant presence in the box and being good on the ball where the keeper is a net positive when it comes to baiting and resisting the press in possession. The high line and sweeping comes after.
So the question should be, do we want to successfully transition into a team that looks to dominate all phases of play or are we fine with ceding control of possession and allowing high calibre opponents to throw the spanner in the works by pressing and counter pressing us in our own defensive third? For me the answer is pretty straight forward, and it's about backing the idea of the manager, rather than backing a one dimensional goalkeeper.