I was hired at a shop who had a large, complex Visual FoxPro application they'd developed in house. They brought me in to write a web interface for it, which I did in Python because there was, thankfully, no Visual FoxPro for Web Apps.
I contented that they needed to start a rewrite in something else ASAP. VFP wasn't going to get more supported as time went on. On the other hand, it was a large, working app, and the pushback was "yeah, someday, but for now we're using it to drive the company".
The discussions were always calm, measured, and conducted by adults. We didn't shout or scream at each other, or anything like that. Both sides had reasonable and compelling arguments to support their viewpoint. But from my POV, staying with the VFP app, with the looming deprecation warnings on the calendar, was insanity. Their point was that rewriting the entire, working app from scratch was also insanity.
It's not like a team wanted to rewrite it in PHP, which we can all at least agree would be madness.