I use JSON. I have used Avro for things in Kafka but I'm not sure the benefits outweigh the negatives. Avro is much more complicated than people think and most folks don't really have a strong desire to learn how it should be used and do stuff incorrectly. Everybody knows JSON and it works with everything though. (Example: so many people just hear that Avro schemas can be backwards compatible but have zero idea that you still need the schema that wrote the message even if you want to read it into a newer one.)

Interestingly, I take the meme as saying a dev is using the wrong types in their serialization format (using strings to store integers) which was my biggest problem with Avro. Mostly from people not using logical types or preferring to use ISO 8601 datetime strings instead of the built-in timestamp-millis type.