The problem is that this position slowly loses popularity and is often replaced with the 4-3-3 or 4-2-3-1 formations for they are reputated to be far more efficient to many teams.
4-3-3 with CDM for better defence and more controlled midfield that can hold together with CMs playibg box to box ( Barcelona basically).
4-2-3-1 for having a high number in the middle and keeping high pressure on the defence, better possesion with the ball and more passing options.
Havertz is somewhere between the two, he can perform well in a mixte position because he does not have a striker/ center forward role, nor he has a very good passing range. Don’t get me wrong, his passing is fine, but not thoes top level passing that are important to open up defences and create chances from his team.
Why the 4-2-3-1 does not work despite Havertz beiing able to play CAM, it is because it is taken by Ødegaard. Therfor, he will usually play CM or CDM which is, by far, not his best positions.
Well grumpy old mas that you are, if overloading matches aren’t enought to players to overcome, with injuries over injuries and close to 0 breaks between club games and international games, 5 subs is actually a mininum to let some key players rest. As a matter of fact, younger generations that are prolific in todays game aren’t getting enought tine to recover, like Gavi who just got an ACL and out untill next season. Vinicius Jr also gor a bad injury. And this also goes to older player like Courtois who also got injured himself and broke his ACL, ending his season before it even started. So stop it sir, giving an opinion with no argunents to support it will only lead to backclash by others.