Having "avro" set by default makes the connector prone to false-positive failures that should not happen (see DBZ-3535). As a workaround, the affected users should opt out of the Avro-specific schema name adjustment.

There are no default values for the key.converter and the value.converter connector properties in the Apache Kafka API. This is because there's no data serialization format that is better than the others, they all have pros and cons.

Based on that, I believe, Debezium should use a similar approach and not provide any default logic for the schema adjustment mode (i.e. default it to "none").

According to DBZ-3899, it hasn't been decided whether or not it's the desired change:

I'm a bit on the fence, arguably, the current default behavior (adjusting for Avro conventions) has a better getting started experience

Let's discuss the pros and cons of changing the default and make the call before the 2.0 release.