Although the Young Justice cartoon was not part of the Bruce Timm DC animated universe that began with Batman: The Animated Series, it was interesting, watching it, to observe how the storytelling in DC's cartoons has evolved along a similar trajectory as it did in the comics.
Batman was made up of mostly standalone stories, and it was self-contained, with scarcely any hint of a larger "superhero universe." Superman: The Animated Series, simply by virtue of existing in the same universe as Batman (as well as featuring appearances by Flash, Green Lantern, and others), began to change that. It was, in my opinion, a thematically simpler work, but it offered greater action and a stronger regular supporting cast for its hero to have meaningful relationships with, both in and out of costume. It traded the occasionally thought-provoking short stories of Batman for superpowered action and light character-driven drama. Years later, the final entry in the metaseries, Justice League Unlimited, was heavy on references to events and characters from almost every work that had come before. That was really not a show you could walk into with no prior knowledge and expect to make sense of. But, from another point of view, it was extra rewarding for those hardcore fans, who had been watching since the beginning and could still keep track of it all, to think that there might actually have been a payoff to their committing so many years of fictional cartoon events to heart and to memory.
Young Justice placed a similarly heavy emphasis on attention to continuity, with almost every hero and villain working some angle that would take the better part of a season to fully emerge. Moreover, even though it didn't share continuity with any previous series and was ostensibly a self-contained new show, it also didn't bother to explain who anybody was, outside of the original core team, despite it featuring at least as many characters as Justice League Unlimited. It pretty much assumed that, if you were watching the show, you already knew what Martian Manhunter's deal was, even though I'd wager that most people, unless they read comics or have seen Justice League, would have no idea who Martian Manhunter is.
I suppose it would be a waste of everyone's time to tell and retell every minor character's origin story with each reboot. On the other hand, this approach does leave potential new viewers somewhat out in the cold, and it's exactly that kind of mentality that has led superhero comics to become so indecipherably mired in continuity that DC has to perform periodic cullings on its fictional history.
Another thing that has kind of gone away, both in the comics and now the cartoons, is the non-superhero guest character. In Young Justice, there weren't very many non-superhero (or villain) characters, period. With a very few halfhearted exceptions, the heroes only seemed to have other masked heroes for friends and lovers. It had become a story about a society of demigods, with no part for ordinary civilians (like, um, the viewers) to play, except as frail and useless children in need of saving.
In the comics, these are trends that have resulted in a readership of, over the decades, an increasingly more insular and older subculture of geeks—people who prefer fantasy to reality and would rather follow fictional characters' lives than live their own. The cartoons, though trending in that direction, thankfully aren't quite there yet (and they've also managed to avoid the distastefully graphic violence that has seeped into even mainstream comic titles), and, for that, I actually should probably be grateful to the executive suits for reminding the writers that these shows are primarily for kids and teens, not for comic book nerds who have studied decades of superhero lore.