Audiences tend to enjoy drama the most. If it tilts extreme in one way or another, chances are, they will be torn. With Superman, their expectations kind of fall in line with an overexposed nature of the Donnerversion, and a collision of worlds caught in between modern Marvel and the TDK formula. They also see Superman as corny/cornball-ish that is outdated.
Captain America worked because of his connection to the overall arc of the MCU. His character was portrayed in the type of Superman realm, but the storytelling also had its dramatic moments. I think Gunn should lean into the "cornball" nature of what people think they don't like about Superman and turn that into a strength on the big screen with great storytelling. As big of a hot rod; electric pole that Gunn is, I think he can pull that off. He can tell a good story. It will have to begin and end there if the DCU Superman takes off.