of course, I am hesitant to say that any of these runners had 'wasted talent' since their careers destroy mine, but for me, I am primarily asking the question, "under ideal circumstances, could they have run much faster than their actual PRs?"
So for people like Granville, Magness, the Dettmans, Lindsay Ferguson, Zoe Nelson, etc., the answer for me is no. They have pretty much run nearly as fast as I would ever expect them to run.
This is in contrast to some of the people on the threadstarter's list like Caitlin Chock, Yong-Sung Leal, and Amber Trotter who I believe still have the potential to run much faster if suitably motivated.