Fair enough, there is diversity of preferences in both speakers and listeners :)

I agree on familiarity polls that you should adapt content based on audience familiarity with the topic.

Whether or not audience engagement is appropriate also depends a bit on the length of the talk. It can be great for a context switch in a 45 minute talk, like a mental reset button for the audience. If you only have 5 minutes it will detract from things unless you want it to be the main focus.