Aviator template: Pixelated home page image (info page)

Site URL: https://goodlivingventures.com/

Have tried exporting the image for the info cover page in a variety of dimensions, resolutions, etc, and no matter how hi-res the original photo is, it uploads at garbage quality (I've tried it with a ton of different images and the same thing happens, so it's not just this particular image that's the problem). Tried deleting all the custom code and the issue persists. Customer service was entirely unhelpful in resolving. Current image being used is attached. I'm assuming that Squarespace is automatically resizing it but can't figure out how to keep that from happening. Anyone have custom code to keep image from getting resized, or other ideas?