Kafka consumer need to commit the offset to kafka and fetch the offset from kafka. Since kafka moved the offset storage from zookeeper to kafka brokers, a kafka consumer does not need to directly communicate with zookeeper, so the new kafka consumer does not need to config the zookeeper.
However, a kafka consumer always needs to connect to kafka brokers (cluster) to send the request to server, the bootstrap-server is just some brokers of this cluster, and using this, consumer could find all the brokers.