Here are some team stats for the Giants' defense for the past few years and their rank within the NFL:
2018: 412 points (23rd), 4044 passing yards (23rd), 1898 rushing yards (20th), 16 INTs (8th)
2019: 451 points (30th), 4225 passing yards (28th), 1812 rushing yards (20th), 10 INTs (27th)
2020: 357 points (9th), 3807 passing yards (17th), 1782 rushing yards (10th), 11 INTs (18th)
2021*: 394 points (23rd), 3740 passing yards (17th), 1967 rushing yards (23rd), 15 INTs (12th)
*through 16 games
So in general the Judge/Graham era has been better for defense than the Shurmur/Bettcher era, which most of us would have guessed. Note that in both the Shurmur/Bettcher and Judge/Graham eras, the defense regressed in year 2 in points allowed. Is this opposing offenses getting used to the schemes deployed by each defensive coordinator? That having been said, passing yards allowed are slightly better this year than last (and much better than in the previous regime), and INTs are up. But rushing yards are way up this year, presumably the combined effect of Tomlinson's departure and Martinez' injury.
For comparison, here are two notable seasons:
2007: 351 points (17th), 3317 passing yards (11th), 1563 rushing yards (8th), 15 INTs (21st)
2011: 400 points (25th), 4082 passing yards (29th), 1940 rushing yards (19th), 20 INTs (7th)
We tend to think of these two Super Bowl teams as two birds of a feather, but really they weren't. The 2007 team had a good defense, the 2011 team's defense was pretty bad except for the INTs (sort of like Trevon Diggs). The 2011 team gave up slightly more points than the 2021 team has through the same number of games, it gave up many more passing yards, and it gave up about the same number of rushing yards. Yet that team made the playoffs and won the Super Bowl, while the 2021 team is the laughingstock of the NFL.
So despite the fact that we have needs on the defense at DT, ILB, and EDGE, really the offense is why this is not a playoff contending team. We're not the shutdown D I'd hoped we could be this year, but we're good enough if the O would just start pulling its weight.