Grimm was entertaining and fun for the first couple of seasons, when it focused on the simple monster-of-the-week stories. Unfortunately too many story-lines about the powerful royal family of vessen, the reapers, the vessen-grimm politics, and the vessen-killing military cult got introduced. The show got ridiculous and annoying.
Nick's wife became a central figure, a lot of insanely off-the-rails things happened to her, and her character was a big drag on the show, in my humble opinion. Claire Coffey was another character that became a drag because she was sleeping with every main character and having kids with them and Grimm became a soap opera about sleeping around, pregnancy clinics, parenting training, and family dynamics.
The last couple of seasons were really hard to watch. Grimm became Dr. Phil's Monster Families.