Message and Event payload validation has been a rather thorny problem ever since extensible data structures (XML, JSON, YAML...) started to be used at scale. In fact, very little progress has been made since the good old days of DTDs. Schema definition languages such as XML-schema, json-schema, or even the OpenAPI schema are unfamiliar to most developers and often result in a rather anemic validation set of rules, leading to a perceived low value, and therefore a lack of interest.
There are three key problems in a schema architecture: