Raheem Morris is a highly regarded assistant coach and has had some success albeit he's never really held the title of Defensive Coordinator. Again, he was DC for the first five games with Falcons and they were not very good, when he took over as HC they got better so was that more of Jeff Ulbrich (now Jet DC) or Morris now could do away with Quinn and focus more on the defense he wanted run as Head Coach.
Again, Morris has never held the title of Defensive Coordinator in the NFL, however, he was a very good DB Coach in Tampa, which catapulted him to Head Coach. In Washington, he was DB Coach for two years under Jim Haslett and they did go to the playoffs and the secondary was pretty solid. In 2019, many wrote about the fact that Quinn turned the defense over to Morris, which lead to a major improvement with the defense and why Owner Arthur Blank decided to give Quinn one more year.
Morris only held the title of Defensive Coordinator in college at Kansas State back in 2006 with excellent results, so IMO, I'm hopeful that he gets his first opportunity to run his defense, he will be successful. Again, I find it hard to believe an Assistant could be so highly regarded, but does not have the goods to be an effective Defensive Coordinator. Plus understood, he runs a 4-3, but I believe Morris will adjust and has the type of experience to do so. The sad part of this is, if Morris is successful, he could be in play for a Head Coaching gig because his overall record is 21-38, not all that good, but not as bad as some that might keep him out of conversations.
Again, I expect Morris to be an excellent DC, just because he's really never had a chance to have total autonomy as a DC at the NFL Level and I trust McVay in hiring assistant coaches because prior to the hiring of Brandon Staley, nobody in the entire NFL had heard of him, however, because of what happened in Atltanta, I do have one eye open on Morris..