The missing thing is interaction between driver and engineers.
With simple cars it might be the drivers that tell engineers exactly what to change or even do it themselves.

In WRC today it likely is much more about telling the engineer what that car does and should do and it's engineers job to translate it to diff maps or suspension settings.


And then there is the decisions and priority aspect. If leadership says the engineer decides and driver just drives it's hard to change much (Meeke in C3, Nandan's phylosophy). Or if they use 50 different dampers and do every test run with a different pair (Hyundai 2018).
For priority it's a problem if one driver wants to make changes that need a joker and don't suit the other driver. (Lappi seemed to have this issues both at Toyota and Citroen, Paddon at Hyundai etc.)