English isn't my first language but self-made seems to me to be about the self as in opposition to others.

And I have always understood the word to be used in that sense.

See the Collins definition (emphasis mine):

Self-made is used to describe people who have become successful and rich through their own efforts, especially if they started life without money, education, or high social status.

https://www.collinsdictionary.com/dictionary/english/self-ma...