In the real world you usually want to extend datatypes and provide new implementations without recompiling let alone rewriting old code (The so called expression problem). This is the raison d'être of complex DI and IoC enterprise patterns and various monkey patching techniques.

I am not sure how flexible the effect approach is. It took decades before static typing became painless enough for rapid agile development. Properly typed DI with safeguards sounds wonderful, but can algebraic effects actually deliver that?