Legacy Systems by themselves are stable over time, The Issue with Legacy Systems is the patching, particial upgrages, Intergration.
Good Designs 20 years ago are NOT Good Designs today. Often times as sections are migrated to the next version there has been no time allocated for general house keeping.
The Goal of a Good Design is not to "Make it Work" but to streamline the system into a lean, stable business working process.
Employees are good at their job, normally that is a good thing. When upgrades, changes designs are required the isolation of departments are a negitive situation.
vendors of the products in use, know how to configure their part without taking a big picture approach.
