You may not be unaware of this but Elo ranking systems are used in a lot of online multiplayer games these days, typically referred to as 'MMR' (multiplayer matchmaking rankings).
And, at least in that context, they're not regularly referred to as 'fun' XD. It's a very good system, but when they're also used to determine who you play in the pool of players it can regarded as a method to forcing players towards a constant 50% win rate or 'forced 50'.
Personally I think Elo is a nice neat system and it's cool to see you making it accessible for other offline use cases.
And, at least in that context, they're not regularly referred to as 'fun' XD. It's a very good system, but when they're also used to determine who you play in the pool of players it can regarded as a method to forcing players towards a constant 50% win rate or 'forced 50'.
Personally I think Elo is a nice neat system and it's cool to see you making it accessible for other offline use cases.