Subsystem is too big of a boundary. GP and GGP are likely talking about function level - which is where I also experience this.

Imagine a situation as simple as:

  foo = ComputeSomething()

Where ComputeSomething() is a complex operation, spread into multiple functions, with many points that can fail for various reasons. If a function four layers down the stack from ComputeSomething() reports an error, this means all three functions above it need to also pass it back as Result<T>, and if you try to avoid the if-else hell, it means the entire call graph under ComputeSomething() will need to be wired with a monadic interface that smartly doesn't execute functions when Result<T> is of Error type. All it does is make you zoom through the call graph doing nothing, just to simulate the default behavior of an exception bubbling up the call stack.