Small chaotic startup that never grew up (15 years atm).
Hosts/maintains a number of apps/sites for various customers.

At some point, someone decides that a CMS would be usefull to maintain the content across all products. Forgoing all sense, reason and the very notion of "additional maintenance and dev" it is decided that one should be built in-house.

Fast forward a number of years.

Ops performs routine maintenance on prod-servers. A java-patch accidently knocks out one of the pillars a 3rd party lib the CMS uses for storing images. CMS basically burst in to flames causing a.... significant incident.

Enter yours truly to fix the mess.
Spend a few days replacing the affected 3rd party lib. Run tests on CMS in test and staging environments. Apply java-patch. All seems fine.

When speaking to frontenders and app-devs, a significant hurdle present itself:
All test/staging instances of all websites/apps/etc ALL USE PRODUCTION CMS. Hardcoded. No way around.

There is -no- way to properly test and verify the functionality of any changes made to the home-brewed CMS.
My patch did indeed work in the end.

But did the company learn anything? Did they listen to my reasoning, pleading or even anguished screams for sanity?

No.