There is no such thing as player progression in their world.
Troy Brown, J.C Jackson, Julian Edelman, hell, even Tom Brady wouldn't been given a chance to develop under them because unless you are a "status" or "name" draft pick from day one (or have stats AFTER being drafted cherry picked to prove your point) that player sucks and is doomed to mediocrity.
No Duggar is not an all-pro safety today. There are no indications however that his development ceiling isn't that high and what he does contribute is something every NFL team needs - a DB that plays "above" his weight and size more like a LB so that teams cannot simply go two TE and run all over 5 DB (now the base) defenses.
He has shown significant improvement in coverage (especially zone coverage) this preseason and will likely be able to turn that understanding into better man coverage in the future.