agreed Defense is not the main problem.. but we see a lot of similar lapses against GOOD teams on D every time we play them.. poor LB play, Safeties always leading the team in tackles, lots of missed tackles, undisciplined play.. soft zone when we should be jamming and playing man.. poorly timed and undisguised blitzes...
offense is definitely the main problem.. defense is not good enough to overcome being put in bad positions too often..
I always get chuckle when people trot out the argument that the defense performs worse against good offenses.
Yes, that's typically how it works. The rules in cfb are overwhelmingly tilted to the offense. Let's go back a few years to 2017. Miamis got a perfect season going into Pitt. Final score 24-14. Was scoring 25 points against Pitts D a big ask? And is 24 points a lot for the D? Time of possession was 36 minutes for Pitt to 23 minutes for Miami. Thats more than a full quarter of football that the D was on the field. In light of that, only giving up 24 points was a miracle (especially given they had a young Kenny Pickett at QB).
Then then championship game against Clemson. Would it surprise you to learn that Clemsons average starting field position was close to the Clemson 45 yard line because the offense was so inept? If I told you before the game that Clemson was going to be the national Champs, had a once in a generation QB, and would start each drive with only 55 yards to reach the endzone, what would you think would be a reasonable ask for the Miami defense in that game? Holding them to 10 points? 20? 30?
As for your last point- what defenses in cfb are good enough to constantly overcome being put in bad positions every game? I'd say at minimum you would need to have a top 3 defense in cfb. With every other team with a D ranked between 4 and 117 (or however many teams there are in FBS now), they are eventually going to give up points if consistently put in bad spots.
Should a head coach spend the majority time and effort trying to get the D into top 3 (where the D is good enough to overcome being put in bad positions) , or should he focus more on getting the offense into the top 10? Ideally, you do both, but if you had to choose one, I'd say he should focus on the latter since it is a more achievable target. If you have the #10 offense with the #25 D, that's a team where the floor is a 10 win season and fans are generally happy. If you flip the script and have the #25 offense paired with the #10 defense, I think the floor is a 9 win season and fans are disappointed. The point is, Diaz can spend all his time and effort in getting the defense to be better tacklers, more disciplined, etc and let's say he even turns them into the #8 defense in the country, I'd say that was a near elite D. Without a top 10 offense, I think that is likely a 9 win team.
BTW- the 2018 defense was ranked #8 in the country.
2018 DFEI Defense Ratings (final)
www.footballoutsiders.com
We finished 7-6.