Unless you want to end up with Adeptus Mechanicus worshipping the Machine God in the MS-DOs boxen, you need to change from time to time. You need to at least be able to open the metaphorical box and see if you can reproduce it in case of disaster recovery.

The more important the system, the higher the existential threat for the organization if you just let it be.

I do understand that it's a thankless job, so this needs to be enforced from up high.