You do know that Maul was brought back whilst Lucas still owned and controlled Star Wars, right? Everything was approved by him. He always said killing Maul in TPM was a mistake.
But sure, blame Filoni.
I've said this before, but the biggest mistake was not setting Anakin as an adult at the start of the Prequels. You only have three films to establish how Anakin went from good to bad and became Vader, while managing to get someone pregnant at the same time in an organically plausible love story. While 10 hours of run time might seem like quite a bit of time, for a fully fleshed out three dimensional set of characters, that's pushing it ( Think of it like a 10 episode prestige TV series ( one hour each) instead)
Was such a waste of Liam Neeson overall. Rebooting him as General Anakin in middle age would have made the narrative much simpler. Then add some flashbacks when he was younger and mixed them into the story.
IMHO, good storytelling is very compact. Think of all the extraneous characters in TPM. Qui Gonn, Maul, Young Anakin and Jar Jar Binks were all excised by the next film. That's a lot of major characters to turf all at once. Terence Stamp, a phenomenal actor, wasted. Sio Bibble, Ric Olie, Captain Panaka, Tarpals, etc, etc. Just a ton of wasted screen time for non memorable characters ( I remember their names because the figures were peg warmers, for basically X number of years after the film came out)
The Sequel Trilogy had the same problem. What was wrong with following a young man who became a Stormtrooper for the wrong reasons and the right reasons at the same time? ( Too much idealism and also didn't want to starve) He finds a survivor and scavenger that he spares and they fall in love and get into a few adventures. What's wrong with that?
Star Wars has to try to get smaller, not bigger. You can have merchandising input into the scripts. You can have action set pieces. You can have cheesy humor. But tune down the stakes a bit. Focus on 4-5 main characters and really develop them. Invest in them.
I remember seeing both of Joel Schumacher's Batman films and wondered why he didn't just steal some scripts from Batman The Animated Series. That's the thing about Star Wars, if you struggle to find something ground breaking, just steal your story from something already established. Stranger Things is a quasi repackaged Goonies. And that's OK. One of the strangest things I've seen in television is Z Nation, on a shoestring budget and stuffed with pretty limited actors, having a stronger narrative most of the time compared to a lot of The Walking Dead.
Can you make something that will still stand on it's own even if you remove the Star Wars specific elements from it?