That's not to say that there are no legitimate critiques or valid criticisms, or even changes or adaptations that should be made defensively.
(I'd like to see more in-quarter adjustments, for example, rather than trying to figure it out at halftime. Although, I think perhaps that has also been improving later in the season.)
In terms of overall performance each year, when looking at the year as a whole, the defense has performed admirably every year overall, including 2017.
There have certainly been stretches where the defense played poorly (Exhibit A: 2nd Quarter vs. Virginia). I don't put that exclusively on Tuiaki, however. That was an outlier, and somewhat on the players as well.
Overall, Tuiaki has been a good DC, and his defenses have been good enough to win most games. The issues in 2016-2019 that led to the underachieving losses were primarily on the offense.
The improvements we've experienced in 2020 and 2021 are because the offense improved. The defense has remained pretty consistent throughout.