Language is more than a formulaic series of spelling and grammar. You have to know how to use it effectively, as well.
I do think that there should at least be a small element [multiple choice exam?] that examines a candidate's comprehension of grammatical structures and syntax, and that grammar and spelling should be given more prominence within exam essays and coursework. However, learning techniques of persuasive language, examining the role of loaded language in the media, learning how to structure creative and formal pieces . . . these are all absolutely vital skills for many careers as a graduate.
English's remit should be expanded, it should not be reduced or re-tasked. What you learn in GCSE English, much like GCSE Mathematics and GCSE Double/Triple Science, is an important foundation for what comes next. I've found myself using GCSE Chemistry and Mathematics in recent weeks as we run over some basic chemistry of erosion - if you'd asked me 4 years ago if I thought I'd ever use either of those subjects again, I'd have laughed at you.