From the Battlefront: Twilight Company novel, which is part of new canon:
"We're in atmosphere," [the Star Destroyer captain] said, embarrassed at his own urgent tone. "We need full power to stay aloft. Any disruption at all - " Star Destroyers were extraordinary vessels, capable of razing mountains and carrying armies. But their mass was measured in millions upon millions of tonnes, and their energy requirements were vast.
Battlefront: Twilight Company Chapter 38
It implies that Star Destroyers are perfectly capable of operating within atmospheres, it just draws a significant amount of power (presumably repulsorlift technology is used to keep aloft, though there may also be ventral thrusters). This is supported by numerous depictions of Star Destroyers operating within atmospheres in Rebels, and Star Wars: Attack of the Clones Incredible Cross-Sections (which is Legends) noting that the massive Lucrehulk core ships use repulsorlift technology to land.