Thanks, that's actually a great article that explains very well why you can't just throw signatures at the problem and claim that fixes everything.

As other commenters have pointed out, the reason Maven central doesn't have this problem has nothing to do with signatures, and everything to do with the fact that all new packages must undergo manual review, which is unfortunately a solution that doesn't scale. (See the "Linux Has Packaging Signing, Let’s Steal Theirs" section from the article you linked.)