Well, I can honestly say I really loved the PSAs on some of the older cartoons. G.I. Joe was well known for theirs for example. Nowadays however, cartoons seem to pander into the mindless set with bright colors and whatever else to keep kids attention, rather than are story based.

However, some modern cartoons were really good and had awesome plots and story arcs. The short lived Thundercats reboot was pretty well done. And Teen Titans, before they became Teen Titans Go was pretty good as well.