Frankly, it's an absurd question. Has Polygon obtained consent from all of the artists for the works used by its own human artists as inspiration or reference? Of course not. To claim that any use of an image to train or influence a human user is stealing is to warp the definition of the word beyond any recognition. Copyright doesn't give you exclusive ownership over broad thematic elements of your work because, if it did, there'd be no such thing as an art trend.
Then what's the studio having its name dragged through the mud for? For using a computer to speed up development? Is that a standard that Polygon wants to live up to as well?
I'd like to chime in the point out that the vast majority of employed artists aren't making anything as creative as cover art for a hobbyist board game. If they're lucky, they're doing illustrations for Barbie Monopoly or working on some other uncreative cash grab. More likely, they're doing incredibly bland corporate graphic design. And if you ask me, the less of humanity's time we dedicate to bullshit like that, the better.
Professionals will spend more of their time concerned with higher order functions like composition and direction. More indies and small businesses will be empowered to create things without the added expense. And consumers will be able to afford more stuff with higher quality visuals.