The whole point in submission, is learning, growing and enhancing who you know you already are.
There are no list of rules on being a "good" submissive.

Realistically, it wasn't that you were bad, it was the fact that you both didn't click together. He saw an easy way to let you go by stating you weren't good enough.

You also stated there were other reasons besides the fact he told you that you weren't a "good submissive", however the reason you posted here seems to be at the forefront.

Sometimes you will click with a dominant, and sometimes you won't.
Your submission isn't a checklist either, you will evolve into what you feel is comfortable by your standards and you will eventually find another to share in that growth of yourself.