Like with all things, Maul coming back was neither good nor bad; it's what you do with it that counts.
Maul was originally NEVER supposed to return. He died falling down the chasm, wondering how the Dark Side could've failed him. Sure, there were some AU comics about him coming back, like him going back to fight Kenobi, or him being preserved as a brain in a jar and menacing Luke Skywalker, but those were else-world stories, not part of the official SWEU canon. Even when they brought him back to fight Vader, they made it clear that it was a clone of Darth Maul, not the original, brought up by some Sith cultists who believed that Vader was too much of a Jedi to be a worthy Sith apprentice. But of course, the main reason such stories kept getting told is because fans wanted more of him and wanted him back.
Initially, TCW's revival of Maul showed some promise. Him going full Game of Thrones with the Death Watch was the height of his story arc, stories like the Son of Dathomir were fun to read. It's just that, once Lucas left, Filoni didn't know what to do with him, so they made him a fuck-up in Season 7 of TCW where he abandons his loyal Mandalorians to go hang out with criminal scum. That makes no sense, since your typical Sith would trade the criminals for the Mauldalorian cultists any day.
Then when Filoni was done playing around with him in Rebels, he killed the guy off in a very nonsensical manner just to jerk off his Samurai boner. Old Ben was many things, but he wasn't that fast to the point where he can out-speed Maul and cut him down like a punk. If that version of Kenobi stepped into the Death Star and fought Vader, the latter's slow-moving cyborg body would ensure that a swordsman who could strike with such a lightning-fast speed would cut him down to size.
What should've been done is either have young Obi-Wan or Darth Sidious kill Maul in the TCW storyline, or Darth Vader kills him at the end of Rebels Season 2; the latter could even give Maul a sort of redemption arc, him holding off Vader just on the hope that the Rebels crew find something in the Sith temple that can help bring about Darth Sidious' downfall.
Or, they should've done what Lucas wanted and keep him around, staying in the shadows, emerging as a threat in the post-Endor era. Shit, they could've brought him up as a new threat in either the Mandoverse or the Sequel Trilogy; as either the head of the "pirate nations", being a third faction emerging in the conflict between the New Republic and Thrawn's Empire, or as the true power behind the First Order. The First Order had a lot of cool upgraded tech that was a step up from what the Empire had, so having a powerful crime syndicate under Maul, who is paying for it, would make the ST more plausible, not to mention making Maul the FO's supreme leader would've at least tickled the nostalgia boners of the fandom enough that it would make more sense than either the revived Palpatine or Snoke.
You could even make it a sort of Clone Wars-style conspiracy where both the FO and the New Republic buy weapons from companies that are secretly run by Maul's criminal empire; where he stokes the flames of war but is careful not to let either side win too much because more bloodshed and chaos means more wealth for him. Then you could make him the face of the evils of the military-industrial complex, as a sort of "Lord of War"-style character. Imagine Yuri Orlov, but with way more power and connections, as well as Sith powers and lightsaber skills. That would make for a worthy antagonist to a SW movie or TV series.
