Multiple dependency versions causes problems but the alternative is pretty bad, too. You can get stuck on older versions of a dependency because newer versions have a transitive dependency that causes a conflict with a different direct dependency

I feel like that's at least a solvable problem that makes itself obvious when the dependency is added. Multiple coexisting dependency versions sounds like a ticking time bomb to me.

Suppose I use a LibraryX that provides DataTypeX, and most of the functions in my project operate on DataTypeX. I later add another LibraryY, because it provides a utility function returning DataTypeX. I should be able to take the result and use it anywhere in my existing code. However, if my direct dependency on LibraryX is a different version than transitive dependency on LibraryX through LibraryY, then it may not have the same functionality. In trying to avoid a problem at compile-time, the package manager has introduced a huge potential problem at run-time.

Yarn lets you reject multiple versions.