Creator of Cicada here. Thank you for the feedback! I've mentioned this in a few threads already, but the reason for making a new DSL for writing the workflows is that YAML makes it hard/cumbersome to express more complex workflows. Using a programming language though gives you more control over how your workflows execute. While there are already plenty of tools that use existing programming languages (ie, Python/TypeScript) to configure workflows, having a custom DSL allows you to make some of the more abstract terms like caching, conditional execution, permissions, etc. more explicit.

To your last point, I have experience with using CD in production, but not to the scale where I have builds stepping over each other and causing issues. I agree that serial builds are important in this case, and is something that I will need to look into (conceptually it sounds pretty simple).