Small, separately maintained packages are bad in a an ecosystem where a final system can incorporate only one version of any given package because it increases the number of opportunities for version conflicts.

Now, it's true that there are some other concerns which weigh in favor of packages being at the minimum useful size, but those necessarily also weigh in favor of a package management system which allows each package to isolate its upstream dependencies without constraining it's downstream users. And not just allows, but facilitates it so that it is the norm, so that dependency conflicts aren't a thing.