You are exactly right. Semantics in the html <h2/p/div/ol/ul/table> etc to define WHAT it is… the css has how it LOOKS.
I have seen some nasty code that defined <p class="paragraph"> instead of just defining the standard paragraph css and using <p>. Of course, if you have a SPECIAL paragraph that you want to give a different look, you can define it with a class <p class="special">.