I can see the issue a few ways:
1) Authoring mistakes would be better if they didn't happen in the first place. Ideally I would like to see some validation happen on packages to prevent many dependency issues - either at package-build time, or at upload time. However this looks
like it takes some time to implement, and likely there would be some limitations discovered in the process of implementing this, such as difficulty of validating multiple version combinations.
2) Unfortunately, there's just no guarantee package owners will update their packages. Packages can be abandoned, or owners can say they just don't want to support the scenario (for whatever reason).
3) There's no license or agreement letting the community or nuget.org to fix abandoned packages that have dependency issues
Personally I think if #3 were fixable that would be kind of exciting, and can go a long way towards mitigating issues 1 and 2!
Ideas along that line - Could package owners opt into an agreement to let the nuget community maintain their package - maybe only in ways which help fix common authoring mistakes? Such as adding missing dependency declarations, or missing framework folders?
Or opt into having their package revert to community ownership if they stop maintaining it?