Yeah, Gunn's success with earlier GoTG films helps a lot, that experience might have helped him while making this film. Plus, Ayer's SS film did some heavy lifting when it comes to introduction of main TSS characters (Amanda Waller, Harley Quinn, Captain Boomerang and Rick Flag) People liked those characters, familiarity with characters also helps the movie even if it's soft-reboot.
Also, while the first movie wasn't great, but it wasn't outright hated (unlike some fans think) it did have fans and got an Academy award and was financially successful, so while the bar is low but there's some residual goodwill there.