Not only do you learn geometry, but you participate in the same understanding of geometry that all later mathematicians started from.
I've always encouraged reading Euclid, Newton, Einstein. In my humble opinion, mathematics is much easier to understand historically, as it developed, and the best historical perspective comes from primary sources.
I must acknowledge, however, that for whatever reason very few people share my perspective on this.
It is indeed a widely held opinion that most (but not all, of course) original works are not the best sources to learn from. Over time ideas become clearer, better explanations arise, etc. Professional educators and instructors are important, too.
