Nothing has changed at the QuickFile end but several different people have recently reported that an update to Safari has changed the way it opens CSV links to view them inline rather than as downloads. If you use the “save” option on the File menu and save the page as a file name ending .csv you should be able to open it as before, or at least use the “import” option in Excel or Numbers.
A CSV file is a plain text file, that’s why many systems use them rather than specific formats like xlsx as they’re more broadly compatible with more different software as well as being amenable to machine processing with scripting languages for users with more technical knowledge.