Often times, I've found situations that you describe (ones where you need to throw infinite developers at to fix) to be a smell that what your "product" does isn't something that isn't line with how your business delivers value. Such things are almost always candidates to be replaced by third party software of some kind.

Maybe I'm wrong though. When you are charting new ground, building new shit that has never been build before--which is what your product teams should be doing--you don't have years long backlogs because you can't see that far out. Good, productive feature work is iterative.

If you can see with a high degree of clarity what you will be working on 5 years from now, it probably means it's been done before and you are better off cutting a check for it.

Hopefully this makes sense :-)