Snape was cursing at a 7th year level when he first enrolled at Hogwarts. Imagine getting to learn from him. Unfortunately, the most we got was Harry learning a tiny bit of Occlumency from him. I wonder what a real protege under Snape would've looked like. Probably impossible though. He was a fundamentally brokenhearted person. Only living for something long gone from him. So he didn't really have enough love in his heart for something like caring for a protege. Seems like since he was 9, the main thing keeping him going was his love for Lily. Lily was why he became a Death Eater. Lily was why he betrayed the Death Eaters.