Totally agreed. That's why I'm not a fan of any new signing until a proper and solid manager is brought and he starts to build his team. Unfortunately this kind of manager that is also able to do the job in a club like Barce is very very hard to find.
Signing a centre forward is pretty straightforward though. Second strikers, playmaking wingers, #10s and midfielders depend more on coaches. Strikers are quite binary, either quality or not - irregardless of system.