Intelligence allows you to solve problems. Creativity allows you to offer solutions no one else would have thought of. If you have one, you can fake the other. But if you have neither, chances are, you won't make it in this field. The difference between a good designer and a great designer is huge.
Good designers are in great demand.
You don't have to be great to make it in this business. Well, that's different. I don't think any teacher can make you a great designer, just as I don't think great writer can be made in the classroom. To be a great writer, you'll have to live and experience all that life has to offer. You'll need to make mistakes, to suffer, to love, to laugh, to commune with other cultures, to expand your mind.