Comment by int_19h

Pure Hangul was used for a long time before then, just not in any kind of official capacity after Sejong. But e.g. most "women's literature" would be written in it.

And back when it was first introduced, it certainly did wonders for literacy. Although it should be noted that original Hangul was more phonemic wrt its contemporary Korean, and the letter shapes were a bit simpler as well.