This is a great thread and reflects some of my own experience teaching games to folk, like my parents, who have more trad games as their background. I have also found they can tolerate some complexity if the theme of the game intrigues and draws them in
In my experience, theme is a real non-event for people without any game background at all. I stock a couple of IP titles on the assumption it would draw interest, but (for example) the superhero games haven't seemed appealing to people who probably watch Marvel movies.
I've found that especially for my mum, having nature themed games draws her in more.
I've definitely seen several people at the boardgame club take on a much heavier game than they'd previously tried, though, just because of the theme.