This is the thing right, when you buy top quality players, they can play multiple systems.
Look at top teams, and their top players VVD, Konate, Macca, Salah can all play in any system. When they sign players its not for one system either.
Arsenal are similar, Saliba, Rice, Odegard, Saka can all play various systems.
If the player has all round ability, you can play 2/3/4 at the back variations of whatever system, they adapt because they are good footballers. Yes, in some systems you need the odd specialist but you dont need 11 system specialists.
You don't even need top players for that in my opinion, pretty much any professional footballer should be able to play in most formations to some degree. You still have to be aware of and cater to/for any significant individual strengths or weaknesses in the team regardless of any given formation/system though.
In my opinion, Amorim now, and Ten Hag before him are making a basic error in that the way they are setting up the team / instructing them to play is often exposing the lack of pace/mobility of some of our players, or not really playing to the strengths of some players in other instances.
That's where adaptability comes in, being adaptable doesn't necessarily mean switching formation, it's about recognising that Maguire, for example, is really slow for a pro centre back, so having one of his centre half partners aggressively step up is going to leave him under pressure each time the ball isn't won back in the first instance, as he's not quick enough across the ground to deal with the consequence of that. Same goes for leaving the midfield two chasing shadows too often, when one of them is Casemiro/Eriksen.
If people genuinely believe a near whole squad needs turned over to play a particular way, that would mean that system/manager isn't right for the club at this particular time.
Yes you can build with the goal of having an ideal player in place for each position, rarely is that achievable though, you'll always have players come in and flop, injuries requiring makeshift replacements, or back ups with different qualities, you need to be able to make that work to show quality as a manager.
For me, a manager's philosophy is never king, they have to be able to balance that with the reality of their squad to be anywhere near successful.
The only sustained success I've seen in my lifetime based more on philosophy than adaptability is Guardiola. And the argument against that is he's done so with pretty much an ideal player in every position and great squad depth, with a tendency to walk away when he no longer has that. Will be interesting to see if he stays at City for any great length of time now.
