This codemod currently does not support legacy decorators, but we have users stuck on Ember classic that use legacy decorators (specifically, decorators in object literals).
The currently-used Flow parser does not support legacy decorators, necessitating a switch to the babel parser. I did a POC spike on switching to this parser, and while it does parse the legacy decorators, there is enough of a shift in the AST format that it causes many of the existing tests to fail. In my spike, I started fixing the code to make these tests pass, but without TypeScript + good AST types, I don't have 100% confidence I'm not breaking things, and working on it is a bit like this gif:
This is a bit of a yak shave.
See also: https://github.com/gitKrystan/ember-native-class-codemod/pull/1, https://github.com/gitKrystan/ember-native-class-codemod/pull/2