Single player isn’t how d&d is played either. It must be 1 PC in the group context to match with your point.
If it’s really that impactful, why the hesitation to show it in that context?
I edited the post you replied to as I may be talking about different things.
Evaluating how a party does in combat is not an effective measure of the effectiveness of a player unless all players have the trait you are evaluating.
Here is an example - If my player is completely paralyzed, permanently, I think we can agree he will be pretty darn inneffective at just anything. Yet the party is still going to breeze through most combats. Sit me up in a corner and go to it. So since ethe party is not really slowed down a whole lot that being paralyzed is "nearly meaningless" to a PC? This is not a good test of this
We can compare players in a party, I am happy to do that. Have a party of 4 and compare the average output of one of them vs the average output of the other 3 of them. But a party of 4 "good" PCs compared to a party of 3 good PCs and 1 bad PC shows us very little.