Just made a black circle in Illustrator and tried to open it in muse, but it comes in a bit blurry every time. The artboard I am using is 1920 x 1080 and I am using the 960 muse grid with 300 ppi raster. I select the circle and drag it to the asset box for export and save on my desktop. Then I drag the desktop file into muse and click to open. I am working on a LG ultra HD 27inch monitor if that has anything to do with it? Hard to tell from this picture, but is very noticeable on my screen.
If you export as HTML or preview in browser, I bet, all looks well, doesn’t it?
As I see from your screenshot, you have zoom your canvas to 200 %! In this case the graphic data aren’t newly calculated – just as they aren’t, if you simply zoom the browser view. Re-calculation only takes place, if you resize the object, not the browser view. Try it, and you’ll see the recalculation by the „Busy“ icon.
To check image quality, never zoom in or out, always use 100 %.