> Just out of curiosity, what alternatives are there to avoid API dependencies?

Very important how the boundaries a drawn. Generally, the more fragmented the micro-services the more API dependencies.

Also, look at the Bounded Context concept.

https://martinfowler.com/bliki/BoundedContext.html

And Conway's Law certainly plays a role.

http://www.melconway.com/Home/Conways_Law.html

> At some level, is it really possible to have a truly decoupled system?

You cannot avoid all the API dependencies, but you can reduced their number.

I'm wondering if the original "API dependencies" comment didn't mean "shared API dependencies". As in, multiple API/services depending on the same shared code/library.

APIs calling other APIs is...well, I'm having a hard time understanding how that could be construed as fundamentally wrong.