Who would you take at #9 in this scenario

While I agree with what you're saying. This seems to be more so having already talented players that performed before him also produce during him and less about him being a linebacker guru.
I missed that part about Staley being called a LB guru. He can’t be a guru since he didn’t have the opportunity to develop a young OLB prospect until his 7th year as NFL coach. He doesn’t have examples of developing many 1st-2nd year guys or transforming many players which isn’t his fault. Staley’s starting 2 OLBs consisted of Floyd, Mack, and Bosa in 6 of 7 years. Floyd had the tools as a former top 10 pick and Staley helped him finally become a good pass rusher in Floyd’s 5th year.

It’s probably more fair to say Staley can continue good production with existing star/productive starting OLBs. He has a good track record in keeping vets productive.