Amen brother!

I had the experience of trying to deprecate a system for which there had been 3 subsequent generations of that system. In the DB we could see the occasional call to the ancient system and that was enough to block the switch off and deprecate of that ancient system. From painful experience we knew that just disabling ancient systems could result in an almighty blowup.

Our problem was that no-one could work out where the calls were coming from. There was nothing in the code repositories and no obvious server source.

The people who concocted the embuggerance had long since left the company.

The implications were that we had to maintain, backup rehearse DR for a system that was of no earthly use to man nor beast simply because it's absence would probably break something critical.