Welcome to the board!
Both Cal Poly's have a ton of advantages (especially in its undergrad department) over the big-bad UCs. For one thing, we are a lot cheaper to attend and have much smaller class sizes. Employers have been aware of the quality of Cal Poly graduates for years, it's just that there doesn't seem to be that much recognition outside of California. Well, in any case, being underrated is in fact a very good thing.
As for liberal arts and social sciences, the "learn-by-doing" approach still works (though many have said that it doesn't quite work on majors that emphasize a lot of theory, e.g. philosophy), and there's always time for Cal Poly to improve that department.