I don’t think what you are describing as heavy is that big of a deal if an external orchestration system is required only for deployment, while the workflow can be developed and tested without a server on a laptop or notebook.

Bringing in orchestration logic in the app layer means there is more code being bundled with the app, which has its own set of tradeoffs - like bringing in a different set of code dependencies which might conflict with application code.

In 2025, I would be surprised if a good workflow engine didn’t have a completely server-less development mode :)