There's two main reasons why Kafka as of today isn't a good fit for implementing event sourcing:

- Lacking support for key-based look-ups: when trying to materialize the current state of an entity, you cannot query Kafka efficiently for just those events (a partition-per-entity strategy doesn't scale due to the partion number limitation, which may change with KRaft in the future)

- Lacking support for (optimistic) locking: you cannot make sure to reject events based on outdated state, unless you apply work-arounds like a single writer architecture