How is that related?
GTO was published in the Shonen Magasine, therefore it's a Shonen.
Shonen has nothing to relate with the DEEEEEP-ness or the epic-ness or any crap you can justificate with. Shonen, Shojo, Seinen and Jousei are demographic parts of the readers.
The magasine which they are published in is the important thing, not your own subjective attributes.