I worked with a short-lived startup which made this exact mistake. I suggested persisting important events to a postgres db, but I was shot down over and over. They were positive it would be fine to hold everything in kafka. There was this notion that kafka functioned fine as a long term data store with the correct configuration (I'm not arguing that), but there was no solution to the lack of... Well, everything postgres could offer. As you mentioned, the lack of velocity really dragged them down. Customers were constantly upset that x broke or y wasn't delivered yet, and each time it was clear that kafka wasn't helping them meet those needs.
Kafka is awesome for what it does, but there are a ton of people out there using it for weird stuff.
Kafka is awesome for what it does, but there are a ton of people out there using it for weird stuff.