I work in digital forensics. You wouldn't believe the misconceptions about "crypthgraphic hashes" and cryptography in general that are around in my area. If everyone took an intro course to cryptography that wouldn't happen as much as it does.
So there you have, one reason to take this course that is not "roll your own crypto" (which you should never do, unless you really really really know what you're doing. And even then you should check with a few people smarter than you to make sure everything is as you think it is.
You are right that the basics are often misunderstood but an Intro course this is not! Knowing what prime factoring is can be interesting if you like maths but definitely not required to understand on a practical level the difference between symmetrical, asymmetrical and things like CSPRNG vs hashing.
So there you have, one reason to take this course that is not "roll your own crypto" (which you should never do, unless you really really really know what you're doing. And even then you should check with a few people smarter than you to make sure everything is as you think it is.