And back to my point, so when Tuchel leaves and you're left with a bunch of 'Tuchel system' players you'll be bang in the middle of a mess United current find themselves in when they decided to take this approach of signing any player the current manager likes on big money then being unable to shift them.
So let me get this straight. First you claim the club are just signing players for the sake of it without any sort of plan 'just because they were available' but when you get called out on it and told there has indeed been a change in philosophy and that the transfer targets are carefully picked to suit the needs of the team, that's all of a sudden not a good thing either? Damned if you do, damned if you don't.
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@Dancfc pointed out, getting in players who fit Tuchel's system is far from a bad thing as long as his eventual successor is picked so he can mostly just continue his work where TT leaves off instead of needing yet another tactical overhaul. Tuchel is a very modern coach so it's not exactly difficult to imagine that players who fit his system to also be well suited for other managers as well who prefer to play a possession-based game with high-intensity pressing.
And who's to say when Tuchel will be gone anyway? The way he speaks makes it seem he's very passionate about the project at Chelsea so as long as everything is going fine, there's no need for him to leave. I also doubt the new leadership regime are going to be as trigger happy as Roman & Marina were so without a failure of massive proportions it's not like he's getting sacked anytime soon either.
To maximize the chances of competing for the big trophies both in the short and medium term, it can only be a good thing the higher ups fully back the manager and buy the kind of players he wants. That is exactly what Klopp and Guardiola have at their respective clubs, and that's the level where Chelsea are aiming to be within a couple of years at the very latest.