AWS managed kafka is great but it's really just Kafka. Confluent offers stuff like topic monitoring, an http bridge, and other services that make kafka more practical to actually use (dare I say, missing features.)

My company uses Kafka extensively. We hosted it ourselves but after a few Kafka meltdowns we decided to go with a hosted solution. We compared AWS's offering to Confluent and at the time found that while Confluent had all of the nice tooling, we'd already built our own tooling to do the same thing, and rebuilding our entire infrastructure was a non-starter. So we went with AWS. It was a drop-in replacement for our own Kafka and it hasn't blown up on us since.

If we where starting fresh, Confluent would be more viable. I can't help but wish that the offerings that are part of Confluent where part of Kafka though. Kafka's lack of the tools that Confluent offers are imo what's holding it back from totally taking over the world.