I definitely agree it's a matter of incentives. Even in an environment with a now healthier quality culture, fixing bugs to bring an old system from 70% functionality to 100% is typically a career dead end.

It's much better to leave it broken and build a new system with 105% functionality so you can take credit for the whole 105%.

And typically, optimists that we are, it seems like completely reimplementing the original functionality will be "trivial" compared to merely trying to understand how the existing solution works.