New downsides such as? And if having to add a few type definitions to your codebase is "way-ay-ay" more effort, I can only assume you really hate typing, as the

New downsides such as? And if having to add a few type definitions to your codebase is "way-ay-ay" more effort, I can only assume you really hate typing, as the mental effort is typically very low (compared to figuring out how to efficiently translate business logic into code, and how to organize code to make it easy for a team to work with over many years as requirements change etc.). There even tools that will generate type definitions for you based on sample data.