Oh I thought you meant the paper quality is bad and dirty because no matter how I see it the scan version is just very low res,
I understand if you prefer the sfx to be scanned but this has actually been explained before the reason they left the sfx as is is because to leave the artistic feelings untouched, and sometimes according to license depends on the mangaka redrawing or removing them are prohibited, and also its to save cost and time consuming you don't need a year to wait for next chapter (but actually official publisher can get a clean paper without texts and sfx raw so its just mostly the matter of aesthetic mostly)

Why is it that the non-official is better and cleaner than the offcial one