Ok the other things you mention above are completely vague, and it is true that is hard to be calculated cause many factors may be applied.

But for what i mention I think it is a pretty straight forward logic: (example defense)
1. Which players contribute on defense
2. What is their defense q that adds to team's defense q.

It is really stupid that my team's defense q is higher when adding the lower in defense Q player.
It is unrealistic.
I have stronger defense using the worst defender (out of 3)

And it is not onky about calculation.
This also disrupts the effect of training.

Is a defender with high defense Q, better than a defender with lower defense Q but higher on the overall Q?
If not training drills, attributes etc etc are sooooooo cosmetic