There are some good episodes in season 7. But, over all the consistency really drops off with too many below average to clunker episodes.

I rated season 7 ...5.7 out of 10.

Has to be the lowest season rating of a classic sitcom I've ever rated.

Yes, they took a decidedly serious tone, almost maudlin at times: Homicide, the hidden Nazi, Barney in jail. Remarkably, I still find humor in most of the episodes.

Here's Hal Linden talking about Barney Miller constantly losing writers, and that leading to the end of the show:

https://youtu.be/B_ZdWzK97fg?si=xDyCven0ecfZoYiF

As an aside, the Foundation Interviews (Emmy Foundation) like the one above were inspired by the death of Danny Arnold. Thousands of hours of interviews with the people who made TV:

https://interviews.televisionacademy.com/our-history

The last few years James Gregory as Luger elevated many without him clunker episodes to at least watchable ok.