It's not an opinion. It is a fact. The W3 says clearly:
"Tables should not be used purely as a means to layout document content as this may present problems when rendering to non-visual media. Additionally, when used with graphics, these tables may force users to scroll horizontally to view a table designed on a system with a larger display. To minimize these problems, authors should use style sheets to control layout rather than tables."
Key word: "
may present problems" . It doesn't always and won't always. So saying no matter what it shouldn't be used for this is nonsense.
And here, "Additionally, when used with graphics, these tables may force users to scroll horizontally to view a table designed on a system with a larger display." Once again,
"MAY". This part can simply be stopped via testing by the coder/designer. And once again, won't always happen. Testing comes into play here.
Just to quickly say though, I do not dislike css and do not think that tables are "better" (I actually use both since my designs are so graphic intensive, tables and css for the table and cell attributes), but to say they should not be used for something as simple as rounded corners is crazy. Not everyone in the world is worried about 100% pristine/perfect code in the eyes of W3. Especially for something so small.