No, it is not that bad. It's actually very nice.

It affords a lot of consistency, is relatively easy to understand (once you're familiar with the convention), and theming allows you to modify all the colors and sizing in one file rather than modifying a lot of CSS

I think the worst that can be said about it is that it is unnecessary, but I cannot see a true downside to using it besides personal preference. It gets the job done efficiently and correctly and that's what's important at the end of the day