I guess I review more than I should. I should write more original articles and fewer reviews. However it comes naturally to me as a teacher and peer review (scientific) reviewer to comment upon what has been written.
Any review must encompass both expression (grammar, spelling, style) as well as content (plot, character, etc.). To do otherwise is to either encourage illiteracy (in the classical sense) or boredom.
Naturally, if you want me to review your fiction pander to my prejudices which are F/f corporal punishment with a bit of bondage thrown in. If I do not read it I will not review it. To do otherwise is to be truly pedantic and academia is too full of pedants as it is.