You know, I used to review fairly often. I think the reason I eventually stopped was because I started reviewing every fic I read in my head. It made reading for fun practically impossible because I always had that nagging little voice going "they're there their" and "that should be a comma, not a period." In that same vein, I was seeking out writers to help and not dedicating much time to drinking in fics that were inspiring to me as a writer. In other words: reading and writing weren't fun anymore. I just got too critical.
I'm working hard to lighten up again this year by participating in NaNoWriMo and just writing whatever my heart desires without worrying about mistakes. I'd also like to dive into some truly excellent fanfiction, but I've been out of the loop for a while so I'll have to dig around some. I think if I can manage to make this whole thing really enjoyable again, the desire to review will naturally follow. There's got to be a balance though.
One last thing I'd like to mention is that if you want reviews, you should find a writing buddy if at all possible. Find someone else who is also writing a story (preferably one you like) that you can trade with and point out errors and problem areas. I've had a friend since the early days of joining this fandom who was writing a chaptered Latias fic just like me, and it was wonderful to simply lose myself in someone else's take on my favorite pokémon when I was burned out on my own writing. And, it was inspirational to boot!