I love defensive battles, I am glad that defenses have regained some power this year, 2020 football was almost unwatchable for me, I got the impression that defense had no tools to stop those high powered offenses.
In my opinion there are several factors why defense has better results this year, one is that referees are allowing hand fighting between WRs and DBs which is a good thing, DBs are not penalized unless they grab opponent jersey or they push with the arm full extended. This is the right way to officiate.
Also bang bang contact between WRs and Safeties is allowed when WR is getting the ball, again this is good in my opinion.
Also zebras are lookin WRs, and especially TEs that create separation by pushing at the top of the route, calling OPI more often than not.
I don't think that low scoring is due only to defense winning, part of the reason is also long sustained drives by offenses.
The good way to check offense "winning" is not how many points it scores, but the success percentage.
For example KC scored "only" 20 points against the Bills last Sunday, breakdown of the drives is the following:
10 drives
2 Touchdowns
2 Field Goals
1 Missed Field Goal (from the 51)
3 Punts
2 Interception (1 in the End Zone after a long drive, defense got the final word, but was "losing" for most of the drive)
So it is true that KC scored only 20 points, but it scored on 4/10 of drives (either TDs and FGs).
This is a remarkable result for Bills Defense, because KC is one of the best, if not the best offense in the league, but the offense/defense "winning percentage" was pretty even.
If the drives were 12, 13 instead of 10, with the same scoring, we should state that defense was really dominating.