I think he’s fascinating and capable. I read American Prometheus a few years ago, which is the biography of him that’s really in depth and factually accurate. One note I thought was interesting was that Einstein was considered from a different generation of physicists and people looked at him differently.
But the book compares Oppy’s contemporaries like Hans Beta to Oppy and reaches the same “no Einstein” conclusion. But my read was that that wasn’t a bad thing, Oppy was extremely capable in physics, but his real natural talent was in bringing out the true insights from others rather than making those insights himself directly, and was otherworldly good at coordination leadership. Which is why he led the Los Alamos project.
I don’t think I view “no Einstein” as a dig, but rather a factual truth presented in the best biography of the man and meant to highlight his world beating talent.