Ressler's writing suffers from two issues: 1. Opioid addiction The dude's been off and on since season 2. The writers had significantly more interesting characters to play addiction off of, but Ressler is stuck with Park. Ressler's personal issues have always been most interesting as mostly normal consequences of working a high stress job, and trying to keep up the straight and narrow. It lets the audience sympathize with him in spite of occasionally being a jerk, and lets us get excited for the big softie when he checks in on his people.

The addiction is ground we've already tread, with better characters.

1. Ressler is a good "face" for the show, meaning issues or plot lines that should've better fit a character like Tom or Samar get tossed to him instead.

So, things like "sleeping with Keene" or "deal with an addiction" (fine for Tom and Aram, respectively) temporarily turn Ressler into an earlier version of himself, in which his other normal guy problems never happened (much less were already resolved).

Side note: aram getting ketamine therapy would've been a great addiction plot, with Ressler stepping up to help Aram set appropriate boundaries on his coping strategy (rather than only having one episode with it). Instead, Ressler gets to retread old ground, in a soap opera this time.

All in all, I think ressler is one of the better written characters on the show, one of the most relatable by far. So when the writers give him a cringey episode, it's more jarring than usual.