I think it would have been much better to design an alternative with the same feature set (i.e. code generation through substitution), but better overall design

I think it would have been much better to design an alternative with the same feature set (i.e. code generation through substitution), but better overall design in terms of hygiene and scoping, as opposed to what C++ has been trying to do by making ad-hoc replacements for some of the tasks you would want to use the preprocessor for, and then admonishing anyone who uses it because of limitations in the replacements. Macros are fundamentaly extremely useful, and the CPP is bad because it's a bad implementation of the concept (as well as leant on far too hard for importing interface definitions), not because the concept itself is bad.