For general workflows, I agree. Doing some DAG system is just a waste of time if you don't have a grounded verifier for every node. If you are going to human verify, why make a dag of subagents and waste time? Keep the dag in your head, the way we all did before LLMs. The dag in your head is also much better.
For specific workflows however, even this is under engineering. If your specific task or family of tasks can truly be decomposed into multiple verifiable subtasks then you should spend the effort to build that system. It doesn't matter if it's technically worse than the other method because it is basically automatic and incredibly cheap. For complex systems this is a lot of upfront work, but if it is done, then the return is completely outsized.
I painted it black and white, but you can of course compose everything.