Kafka IO in dataflow job is not able read more than 1.5k messages per second with workers equal to the topic partition

Question

Kafka IO code on dataflow job:

 PCollection<KafkaRecord<String, TopicMessage>> topicPCollection = p.apply("Read from topic", KafkaIO.<String, TopicMessage>read()
            .withBootstrapServers(options.getKafkaBroker().get())
            .withTopic("TOPIC_NAME")
            .withKeyDeserializer(StringDeserializer.class)
            .withValueDeserializer(TopicMessageDeserializer.class).withConsumerConfigUpdates(
                    new ImmutableMap.Builder<String, Object>()
                            .put(ConsumerConfig.GROUP_ID_CONFIG, "groupId")
                            .put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, true)
                            .put(ConsumerConfig.FETCH_MIN_BYTES_CONFIG, "104857600")
                            .build()
            ));

I have configured 50 partitions and 50 workers on the dataflow jobs, but still, it is unable to consume more messages from the topic.