Actually, Steve has great character growth in S1. He started out a stereotypical horny teen, but he acted when it counted at the end and came back to fight off the Demogorgon. IMHO, that was the first real test of his character, and he passed with flying colors.
Agreed he had that moment but I loved the way his character really changed and molded during season 2 with Billy basically knocking him down a peg and everything else