Yes, some type of CSS “parent selector” would be nice. eg.
td.the_val < tr {
font-weight: bold;
}
<tr>
<td></td>
<td class="the_val"></td>
But alas there is no such thing and AFAIK the technical difficulty involved means there never will be.
However, JavaScript parentNode() is capable of going up the DOM
I would not want “every element to have every possible class value” like some apps do (cough WordPress) but I think if adding a class value to an ancestor element so that CSS could “drill down” would help there is a good chance it might just happen à la pr welcome