This could so easily be a rant.
But I present to you the following, and I'll try to restrain myself from pointing fingers.
When you look at code over a long period of time, you can see any given package as either healthy, sick, or dead.
Healthy code has a tested and stable implementation, with few to no CPAN Testers FAIL entries (N/A are permitted). Over time, it will replicate (in a fashion) by becoming dependencies for other packages.
Sick code tends to have weird bugs (rt.cpan.org entries) that hang around for a long time. Very sick code fails on entire platforms for long periods of time (bad CPAN Testers results) despite claiming support for it.
A variation of this is necrotic code, that can't change for legacy reasons but is terminally sick. In the best cases there is a better replacement and we can just cut out the code that uses it and replace it with the newer code.
Sometimes packages die from a more conceptual point of view, because they are implemented based on an incorrect premise. You tend to be able to recognise these from CPAN Ratings, where the pattern of ratings starts out positive but gets worse over time as the second and third-order effect of the incorrect premise takes hold.
You also tend to see people adopting it enthusiastically, and then later abandoning it with equal enthusiasm (as we've seen for things like prototype.js).
These can often be fixed, if often reluctantly (*cough* Module::Build and PREFIX *cough*)
The one common factor leading to the death of packages, and indeed entire projects, appears to be continuity.
That is, does the project keep going, and is there sufficient hours of work being put into the project to keep it alive, growing, or removing bitrot, or correcting conceptual mistakes, and so on.
Because if you don't ensure continuity, and ensure it in advance, you're only one step away from all your work being completely pointless.
This is particularly important in Open Source projects, because Open Source projects aren't typically income-generating. The state in which someone is working on an Open Source project without being paid is quite rare.
So it's unbelievably important that authors of Open Source projects harvest those moments in which someone is willing to work for you for free. Things like co-maint permissions and version control access and being willing to give up some amount of creative control once you can't work on a module as much as you'd like to.
Or all your work will ultimately be for nothing.