Good point.
Any new product should have $X bugs/month added by the current developers so that future developers can indicate 'signs of life' by fixing $Y bugs/month![1]
TBH, once a product reaches whatever goal the founders set out to achieve, adding features can only make it worse, not better. Bugfixes, refinements? Sure. Extra features? Can only heighten the learning curve for newcomers in the future, even if the incremental learning curve added is small.
[1] With suitable values for $X and $Y so that a project can show slow and steady improvement in reliability, until the inevitable rewrite 12 months later.