Tuchel has proven he can win the biggest prizes at the highest level playing good football. He didn't manage to win the league against a freak invincible team.
His career has dwarved Ten Hag's to date which is why you finding it laughable to say he is an upgrade is absolutely absurd and proves a clear bias.
Who has shown more ability to be a manager at the top level to date, Ten Hag or Tuchel? I'm genuinely fascinated to hear your opinion.
Tuchel has achieved more than Ten Hag has, of course this is an objective fact and not even worthy of discussion. Just like Jose Mourinho has achieved more than both of these managers, which is an objective fact and not worthy of discussion. We however, will not go for Jose Mourinho, and an argument was rationally made that we should have never gone for him in the first place.
Tuchel has developed a reputation of being abrasive and difficult to work with, he does not adapt to the people above him and that's where things become extremely dicey. Moreover his astounding failure at Bayern makes one wonder (rightly) whether he's the right manager.
He did really well lifting Chelsea half way through the season and winning a Champions League, just like Di Matteo did. But with Chelsea he operated a 5 at the back system that was incredibly dull, and that does categorically not work at Manchester United. Moreover him scoring a lot of goals with Bayern in a much lower standard league with a generational striker to his hand doesn't mean nearly as much as you want to claim.
What is massive here, is that Tuchel has 1) chronically fell out with his superiors and 2) really underperformed with Bayern in both seasons he was there. He has not looked convincing as a Bayern manager at any point in his tenure - he would have likely been sacked at the end of last season if Dortmund didn't bottle it on the final day and allow Bayern to win on goal difference.
Do I objectively think Tuchel is a very good coach? Yes. Do I think he's a coach that can make immediate impact? Yes. Do I think its beyond reasonable doubt that he'll fall out with people above him? Yes. Do I think he'll do about the same as Ten Hag in silverware? Probably not.
I don't see Tuchel as a manager worthy of sacking Ten Hag for. I don't see Poch as the guy either (and I do like him, he's just bottled too many things in his career). And McKenna is completely unproven at top level. The market is really thin, and I don't see Poch moving anywhere. Giving Ten Hag next season isn't as terrible an idea as it sounds. He's not a fraud by any stretch and there's reason to believe he can tweak the open tactics from this season under a game model suited to Wilcox. Poch is probably going to hang around and wait for his moment, you get another season to judge Ireola and yeah you might miss the boat on McKenna but there may be movement with Ancelotti at Real, there maybe movement in other places too.
There were two major issues with Ten Hag - 1) his style was too open and he's changed it but the league was well gone by then, and 2) he had crazy injuries which made his suicide tactics even more exposed.
He is very capable of tweaking his approach, because he's a good coach. What we already know about him is that he's a winner, a man that the team is clearly behind and he sets high standards, whilst adapting to shitshows. Tuchel doesn't do this.