The thing with Aquaman is that I suspect general audiences are, in fact, still going to be impacted by Super Friends or how he's been depicted outside comics on who he is. Ask someone out there about Aquaman and they'll probably say something like, "Doesn't he talk to fish or something?" Not realizing he's the King of Atlantis and has powers and abilities that make him a bit of a badass on land. Hell, even when Smallville introduced him they did it with a heavy taint from Super Friends.
As for my "weight of the past" when it comes to audiences, I think I was misunderstood.
General audiences are afraid to go into movies that may have story behind them they're not familiar with. Many people still will say things like, "I'm not a Star Trek fan but I did like the movie with the whales." Why? Because that's the one movie that was approachable to the most people as it wasn't as bogged down by the genre/setting of Star Trek. All of the TNG movies were made to be as stand-alone as possible to not draw on previous movies, the series, or the current stories on the still-going series. Again, to reach a wider audience.
It's unlikely general audiences would have even bothered with The Avengers if the previous stand-alone movies hadn't been made. Because they would not have known all of the characters in this movie, what they can do, and so forth and simply thought you'd have to be into the comics to "get it."
The individual movies were the way to go because it introduced all of these characters, told audiences who they are, what they can do, and helped to build this "new world." (The MCU.)
If they just went ahead and made a Justice League movie with several DC heroes in it audiences would be intimidated by it. Because aside from Superman and Batman (both of whom are well-known enough that even the most casual of comic book genre fans know who they are) and possibly Wonder Woman people wouldn't know who they are, what they can do, and what their past and motivations are. So either the movie would have to draw from the comics for the pasts -relying on an informed audience to "get it", or bog down the movie with exposition to introduce the characters.
The average person off the street doesn't know that Aquaman is the king of Atlantis and has incredible powers that can match him with Superman or Wonder Woman on land, he's "the guy who talks to fish." Most other DC characters are going to pretty much have the same problems. They need to be introduced in order for a JLA movie to work.
That's why Marvel worked, especially since they used characters who aren't very commonly known to most audiences. Hell, I'm not a Marvel reader so I was a bit uninspired by an Iron Man movie but it was knocked out of the park. My only real exposure to Thor is Norse Myth and the little girl in "Adventures in Babysitting." Another movie that did a real good job of introducing him.
I'm a comic fan and reader, and I really do believe to "do this right" DC needs to introduce their characters in their own movies. Screw comparing it to Marvel. Just doing the team movie alone is going to get them compared to Marvel. Might as well put all of their chips on the table and do what Marvel did rather than trying to re-invent the wheel.
Besides, if they're to do a Justice League movie I'd say Aquaman, Wonder Woman or whoever else they use deserve their own "origin movie."