I know you didn't ask, so feel free to ignore me completely, but I've had a bit of luck by starting with a completely different genre that forces a need for different rules. If you're playing basic 5e and can switch to something where you're running a ship then a rules change makes sense since a ship is expected to have different mechanics than a PC. Once they see that other systems have rules that make sense for and support the genre, they may be more invested in understanding them.