Software engineering is said to be programming over time.
Many free software funding models ignore this aspect, funding only new feature development. Projects that are decades old often need more maintenance work than new feature work.
Maintaining old projects also needs more expertise than starting new projects or adding features to an existing projects (at least in well structured ones).
This recent blog post from @AntennaPod is a good illustration of this.
https://antennapod.org/blog/2024/05/modernizing-the-code-structure