What exactly are you pining for? The strength of the 2019 team was the offense not the defense. The Defense was solid but they didn't exactly shut teams down either. Look at the scores from those games, especially the early season ones where we won close non-conf games.
The current defense leaves a lot to be desired right now, but it isn't like we went from an all-world defense to a bunch of scrubs.
The biggest issue right now seems to be teams making adjustments to us at halftime and exploiting the D in the second half. We held Ohio State to 10 in the first half and Miami scored 3. 2nd half defense in both games was atrocious.