Thanks for reporting this!
Do you use a high DPI machine? (like Surface tablet).
If yes, then it's recommended to compare the original with the 2x rendering. To do that, export for Web platform instead of Design and resize the generated 2x png image to 50%.
Also, I noticed that document zoom (upper right corner) is higher than 100%. Raster images look pixelated at higher zoom.
Do you see the same quality loss when comparing at 100% zoom?
Yes, I did use the export for design, while maintaining the WEB x2 loss of quality is not present. My respect Mihai!
"The problem" is solved.