Casey Winters takes the product/market fit model further in his post Feature/Product Fit:

Every product team tries to make their core product better over time. But sadly, at most companies, the process for this is launching new features and hoping or assuming they are useful to your existing customers. Companies don’t have a great rubric for understanding if that feature is actually valuable for the existing product. This process should be similar to finding product/market fit, but there are some differences. I call this process feature/product fit, and I’ll explain how to find it.

This is a great way to approach ongoing, consistent improvements to our products. Casey’s practical checklists and advice are worth reading and bookmarking.