It depends how you define success. I like to write on Medium mostly because it mades me clarify my thoughts and attempt to make them comprehensible. Occasionally I hit a nerve and get a lot of readers. Mostly, it doesn’t happen.
If you notice, most of the people who make money are the ones who were making money as a writer before they came to Medium. There are a lot of accomplished journalists and artists here. That’s true in the rest of the world also. If you have a “platform” you will do better. But remember, there seem to be a lot more writers than readers on Medium — and even fewer commenters.
Then there is the task of balancing quality and quantity. How often can you create an interesting, unique post, or is it better to constantly fill the space with your somewhat brilliant thoughts and hope for the best.
But, as the good doctor says, keep the positive attitude. Do whatever fits you. Don’t get discouraged, even Kafka had a tough time getting published. It doesn’t mean you’re not talented. But, keep your day job.