This is of course just my opinion, but I'm pretty sure what kills off a legacy project is whether the organization is committed to maintaining it rather than it

This is of course just my opinion, but I'm pretty sure what kills off a legacy project is whether the organization is committed to maintaining it rather than it being some kind of property of software itself. Minimizing churn is just one aspect of that commitment. If the project was always a mess it probably wasn't as important to the business as the developers believed.