Read carefully. There's a big difference between developing a database and developing an app that uses a database.

If you're developing a database, you should use property-based tests to ensure that your database behaves as expected (ACID reliability, etc.). If you can formally verify parts of your database, you won't have to fuzz it, because it will have been proven correct. But if you're developing a CRUD app that uses a database, there may be no properties of your app at all that are worth fuzzing.

Similarly, if you write a library that parses Markdown, you should write property-based tests of it, and fuzz it. If you use a library that parses Markdown, you should pass it your Markdown, and let the library handle it.

E-commerce apps typically don't need to do any non-trivial parsing. Effect-free logic is likely to be ~1% of your code base, or less.

This is why we keep talking past each other: the techniques that make sense for real-time operating systems don't make sense for an e-commerce app, a line-of-business admin dashboard, or a single-player game.