there's been other threads on this site where people talk alot about how much they learned in either or both their compilers or operating systems course. This rings true for me -- the value of my first few semesters of CS was that it prepared me fully to tackle a short list of really helpful courses. Honestly finishing the major wasn't all that much more helpful (in terms of what I learned), but the degree itself has worked out fine.
One last thing, but for me there was a sort of retrospective signal -- I did have a second major and other areas of study, but eventually I realized that I had always saved my computer science homework for last because i found it the most fun, and gosh, maybe that was a hint of where to build my career. So to make it more general, the other "use" of a bunch of mediocre CS coursework is that you can gauge your own interest level. We're all built differently, but honestly taking a wide variety of courses to learn what you're interested in while in your late teens / early 20s isn't such a terrible thing (if you can do it without too much debt).