I think kid fics can be written wonderfully but for them I have a hard time seeing it.

Pretty much this. Why when I was prompted to write a kid!fic in this year's Secret Santa, I ended up with a rent-a-kid. Silver Bells (http://archiveofourown.org/works/1121312) -- charting their (respective and ultimately positive) responses to this little life they'd been entrusted with, without having to suspend my disbelief high enough to think that a kid would fit into their lives permanently.