He's a strategy: get a copy of Microscope by Ben Robbins, and tell them you're going to use it to create the world/setting for your next campaign (this is something many people do). Once they've played, ask them to do a stars and wishes, see what they say (I would be extremely surprised if they don't love it).

Then point out that Microscope is a ttrpg, just a wildly different one to D&D, and that there are thousands of other games that do weird and interesting things with mechanics that most trad games can't even dream of doing (e.g. some examples: Everyone is John, Ten Candles, Fiasco, Wanderhome, We Are But Worms).

Viditya Voleti's A Land Once Magic is another good option that you can do this with, and it's a bit quicker and easier than Microscope.