Looking for an engineering crucible to forge myself into a better engineer

Hi! I am a TVC at Google and spend my day writing code for an Android app and keeping backends/frontend in a healthy state. I am looking to improve my technical skills and gain mastery. I want to be used and abused to get that experience. My end game is to get a job at one of the larger tech companies mainly due to the flexibility and scale (I feel.more comfortable in large organizations) but I figure there is still part of the road to walk to get there. I am a very poor interviewee. I have been rejected (is this the most appropriate word?) from Amazon (2x) Google(2x - the first time it was borderline), Microsoft(1x), Lyft(1x) during on-site rounds. Is there a good place (company, school, retreat) that can serve as a crucible where I can be undone and reforged as a much, much better engineer? The goal is to become the best engineer I can and secure a better job. For background, I have a non-CS undergrad (engineering) degree and a master in CS. I have some time constraints due to family obligations that make it easier for me to switch jobs and forge myself into a better engineer than spending time at the end of the day to practice and learn. What would you recommend?