If you roll your own crypto and say, "that was a fun learning experience" and write a blog post about what you learned implementing AES in some novel way, nobod

If you roll your own crypto and say, "that was a fun learning experience" and write a blog post about what you learned implementing AES in some novel way, nobody is going to show up and tell you not to roll your own crypto. If you roll your own crypto and then deploy it in a production system, then you are putting actual users at risk.