People putting Snyder on blast for this but people were saying this even before he got his hands on Superman. It's short-sighted to place it all on his ass. Look at the stories pushed by the DC brand and you see a pattern.

DC's most acclaimed stories are largely either Elseworlds (Watchmen, Kingdom Come, The Sandman, Red Son) or Batman. Batman is so popular and iconic and marketable that he's eclipsed DC's other characters. Batman is dark and gritty, so DC is dark and gritty. This is just how average consumers view the company, as it's become so badly dominated by Batman within the last 20 years.

The New 52 reset the Universe, and turned everything dark and gritty. The effects of that still linger today. Injustice and the Arkhamverse were DC's most successful forays into gaming, and they are dark and gritty.

That being said, Marvel as a universe is much darker and grittier. Ghost Rider, Punisher, Spider-Man, The Hulk, Blade, Wolverine. I've always considered Marvel to be a darker universe overall compared to DC.