I'm going through them all again now. Currently in season 2. Will circle back once I get into season 5.

But, at this point, I can say, even during its prime, this show had lots of pace and timing issues. Often, the writing and direction were brilliant, but it's hard to sustain brilliance indefinitely; just as often, there were awkward moments, moments with a lack of rhythm, pace, sheesh, when it seemed the writers just didn't know how to advance or resolve a scene, moments that just didn't work...but you hung in because the next brilliant moment was not far off. All shows have them, but it's far more noticeable to me (and frequent) in this show than in any other.

In other words, this show needed all its chemistry just to do what it did well in the first place; once Hartman was gone, what were the odds they could insert a new face and get the timing down when it was so difficult to nail in the first place?

Skimmed through season 5.

First impression is that, indeed, it wasn't the same.

It is tough to catch lightning in a bottle in the first place. When main characters change, it's really hard to duplicate. (see Two and a Half Men).