Fanfiction is only considered cringe because it’s a predominately female thing, especially by young women. Anything strongly associated with women is automatically given less value in society (until a man does it).
If anyone does find it, just say you want to be a writer and writing fanfiction seemed like an easy first step. Some actual writer have admitted that they started this way. Plenty of writers have published their own Sherlock Holmes stories too or sequels to other classic works.