I agree, the analogy is shaky.

Adding extra components to you solution, like Kafka, adds complexity, overhead, maintenance etc. While adding an extra rocket stages reduces load, because you get rid of the extra rocket element as soon as it has been used. It will make the rocket lightweight once it is in final orbit.

The intention is good, but the analogy isn't right, it's actually the opposite :)

I never like analogies in decision making, especially when done by management who don't understand technical details of a solution. "Sure we need Kafka, we can't send a tank ship into space can we?"