i think it also falls into a weird area of it being a kids show about kids... and usually those weren't very compelling. i know a lot of people who swear by recess, and by all accounts, it seems to be a good show. i never watched a whole lot of it though, so my outsiders perspective is that it's a fairly simple show that had characters fitting into clean archetypal roles, similar to doug or even rugrats. this impression is probably not correct, because again, i haven't actually seen a lot of the show. but if someone had taken a glance at it, it probably looks shallow and childish when it's anything but.
as an example, doug walker (the nostalgia critic) did an episode on nicktoons. to prepare for his review of hey arnold, he watched 'downtown as fruits.' that was it. it's not a bad episode, but it's hardly representative of the show as a whole, and does fit into what an outsider might expect of a kids show (oh they're dressed as fruits and they're downtown... how zany). but there are far, far more that better showcase the music, writing, art, and acting.