The show was supposedly about Red chasing blacklisters with FBI + Liz...
[Show spoiler]S1 and even S2 was pretty good along those lines. In S3 Liz didn't do anything except for complaining a lot, whether or not she had a reason for it. Everyone had to dance circles around her, and as far as chasing bad guys or doing any actual profiling (which was her job description in the beginning) she didn't do anything interesting. I really couldn't care less about her on and off romance with Tom, their child and whatever other soap opera crap writers threw at us.
What's worse, because Red has to play daddy, he's not doing what's he's really good at - getting bad guys with elaborate combos and cool speeches. Instead he has to apologize again and again, beg her not to get married, etc, etc...
To be honest, I was already sick of all the drama surrounding her. I am sure they will bring her back to do more complaining, but if not, I won't miss that character, not after S3.