They need to be careful with how much of the story one needs to know from watching the cartoons.
When the prequels came out and General Grievous appeared I was like who the fuck is this stupid Jedi killing droid, why do they fear him, and act like they already know him?
Apparently he had been fleshed out in the cartoons.
That I didn’t watch.
Well, to be fair on that front- Grievous wasn't exactly fleshed out when Sith came out. He was just a 5 minute appearance in the Tartakofsky animated Clone Wars movie.
All
that cartoon did was answer why he was an asthmatic and coughing. The CGI animated Clone Wars show did in fact flesh him out a bit more. BUT - not a ton. They had one ep where you sorta see how he got the droid body. After a season or two, they decided to kinda shy away from Grievous being the big-bad along with Dooku because of the Sith movie. You know he's still alive and running around in Revenge of the Sith, so he couldn't just keep getting away at the last minute a la Doctor Claw from Inspector Gadget.
But for Maul, yeah they sorta took him outta the trash that Lucas put him in, and gave him an origin, purpose, characterization, a reason for existing and even a brother. I understand your argument though. But like famicommander mentioned - the shows have been way better than the movies.