Keep in mind that I wrote this comment while streaming, and that running streams does make use of one's graphics card.
That said, I tested both the Steam version and the version here on Itch without the stream software running. In both versions, the game runs smoothly at Low settings. At high settings, it starts at a 30+ framerate but begins to drop as the game begins demanding more of my RAM.
That's why this likely hasn't come up before; this performance issue at low settings is something that streamers will deal with due to having to run software that is pulling resources that the game also wants.