That is pretty optimistic.
The bigger question is whether having a top 5 run game matters much anymore. Having a terrible run game is an impediment, but the rules favor teams that throw the ball now. Just as it does not really look like being a top run stopping team matters much at all now, just don't be terrible stopping the run and you will be fine (or be terrible, like the Rams and still win a SB)
As the NFL continues to feel that building QBs into stars, marketing them, and using their success to determine how teams succeed themselves - it does not feel like there will be rule changes to de-emphasize the QB.
Which means passing and stopping the pass are going to continue to be harbingers of success. With more mobile QBs, you can even pour less money into OLs (as Seahawk fans are painfully aware of).
So would a team with a top 3 Defense and top 5 run game but average QB even do anything in the playoffs?
You could point to the Rams, who have a fantastic defense, a very good but not elite QB (but all the surrounding talent for the passing game). So maybe you don't need elite QB play - you need a tremendously good QB and phenomenal D to mount that approach.
But a top 3 defense and top 5 run game with an average QB probably makes you closer to the Titans than the Rams.
(Now 'what works to win a championship' changes. I get that.
It was not long ago that NBA teams that shoot too many 3s, could never win a championship because in the playoffs things slowed down and those missed 3s turn into long rebounds + fast breaks. Ostensibly. Then the Warriors made it look like you HAD to shoot 3s to be successful.
It wasn't long ago that the key to success in the NFL playoffs was great lines. Dallas won 4 SBs that way. But those are all symptoms of rules changing.)