I would say yes, you can become a millionaire with Steemit, for you to achieve this goal you need to work a lot, you need to automotivar, to believe in yourself and create relevant content for Steemit community.
Try to write on general topics, topics that arouse interest in the community such as: technology, blockchain, cryptocurrency, fashion, culture, music and others. No doubt that in the coming months we will have many millionaires made with Steemit.
Disclose Steemit where you can.