Modding is a lot more approachable than making a whole new game. The only issue is most games aren't moddable. Some people still try to mod games that don't support modding and that's where you're likely to run into copyright issues.
I think its both. Modding has become harder, and making games easier. At some point they are close enough to parity that it just makes sense to put in the extra effort to avoid all the tertiary issues, like copyright/trademark violations.
