Thank you for this. I completely agree with you. Unfortunately my essay had a different focus but maybe I should try to interview people just on their personal feelings and see how that -- less cerebral -- perspective would be different...
In my opinion, big groups are the cancer of life sciences academia. It's not just me who thinks that. If you look into all the organizational research that HHMI did prior to setting up Janelia Labs, they essentially concluded that CSHL, LMB and Bell Labs were so successful in the past because groups were small and all funding was internal (which implies you no longer need PIs, you can go back to classical professors).
The vast majority of the big PIs I have worked or interacted with (and that includes Cambridge, Oxford, EMBL, Karolinska, MIT and other places) are pure rent seekers, literally. They bet on some postdocs or PhDs and simply stamp their name as last authors if there is a publication. However, they rarely have any insights on what is being done. Sometimes they don't even understand it at all. So no value added, just profit. Unless you count as value chairing conference calls, calling editors to negotiate publication terms or discussing funding with agencies (most grants are actually written by senior postdocs, despite what author lists indicate).
That's when things go well. When personal issues pop up, they can screw up their subordinates big time. I have witnessed this many times. After all, grads and postdocs are just pawns in their chessboard.
Such an organization is at odds with classical academia, where your professor (not PI) was your mentor and you would engage into endless discussions about science with him. Other fields retain some of this approach, but in life sciences it is lost.