Perhaps they thought it would attract more female viewers to the show, I don't know. But it's definitely the worst part of the show.

I would lay 95-99% of the blame on the writers.

I often get the vibe of watching some sort of mashup between veronica mars and 24 when I watch this show. This is not not even subtle most of the time, the writers saw some Korean drama or something.

Excessive amounts of big loud guns bang banging, into an interpersonal character revelations with some loud music(and often times some not so subtle foreshadowings going at it :p)

Something else I wanted to note is the way her character devolved in some ways over the seasons.

She was a rookie FBI profiler with minimum field training, IIRC she also has some license for counseling children and she also had a life outside of whatever is going on between her and the task force.

Beyond very few episodes (The Stewmaker, The Deer Hunter, Lady Ambrosia and a few others that I missed), it's very hard to tell any of this. I know it's because this isn't the "Elizabeth Keen Show" and also because 80% of the events revolves around Reddington. In recent times, aside from when she goes all "amg I love tom ;)", it's often hard to tell Liz apart from some jackass fbi agent #39. This makes Liz a key character in the plot that we have hard time feeling attached to and it's very easy to right her off as the some dumb weman.

tl;dr Liz doesn't get enough screen time considering the importance of her role in the storyline as well as her status as one of the main character.

This mostly irrelevant to the topic but I felt weirdly attracted to pregnant-and-weddingdresswearing Liz shooting shit up, and I have no idea why.