If you define “specifications” as a formal document with that title atop, then you’re right.

If you define it as a description of what needs to be built then by definition you can’t build what is not described.

User stories are a type of specification. “Build me a Facebook clone” is a type of specification. A well-refined Figma doc is a type of specification. They all specify what needs to be built at various levels of fidelity.

You need specifications.