To truly judge a HC you need to see them with a capable QB (or at least a QB who's not completely overmatched). A bad HC can't win with anyone at QB (see Bowles with Brady, Garrett with Prescott, just about every HC Rivers had, etc).
Walrus wins when he has one (prime McNabb, A. Smith, Mahomes) and loses when he doesn't. Tomlin did plenty of winning with Ben (though many think not as much as they should have) and flopped horrendously whenever he got hurt (which was often). Sean Payton, same thing as Tomlin, probably worse. He won some with Brees (though a LOT less than he should have), and was hopeless whenever Brees got hurt.
Can't get a full measure a boxer's ability when he's forced to fight one handed. BB has more than proven his mettle when he fights with 2 hands. The problem is that this past year (and perhaps for a bit longer), he's put himself in a position to fight one handed, and has no one else to blame.
Fixing the Patricia and Achord fiascos will go a long way to letting Bill fight with two hands again.