Rule #2: Unions can be overthrown from within.
It's happened repeatedly.
If you want your union to be more democratic, or more militant, or whatever there is a path to do it. You can look at the history of Unite All Workers for Democracy: https://uawd.org and the actions of the Chicago Teachers Union described in No Shortcuts: https://global.oup.com/academic/product/no-shortcuts-9780190624712?cc=us&lang=en&
Now think about the things they are standing in opposition to. Can you change them the same way?