“My hunch is hiring these new engineers who reinvent the wheel and are not very knowlegeable about what works and does not work from past engineering lessons.”
That tends to happen when development times span across generations.
Most people just don’t understand this even when you explain it to them. People have memories, companies do not. Just because something has been documented does not mean it has been remembered or understood. Most of the time, if there is a really good project manager and chief engineer, the project dies when they leave. Only a few people have the capacity to absorb and remember the whole project in a way that understands and manages the gearing AND have the drive to push though obstacles..