To my mind, that game has a major problem.
New players join leagues without taking care where they go at. And they go into leagues with inactive hosts, play with inactive players and then become inactive players as well.
I saw somewhere in the forum that inactive accounts for 28 days get kicked out of their leagues. That's a good thing. That's why there must be something like that for leagues too.
Leagues with inactive hosts for 28 days should be unjoinable. So people in those leagues are stuck together and no one else can join them.
And then at the end of the season, you kick the active players (inactive players for 28 days are kicked during the season) out of the league so you can delete it and they will have to find a new league to join.
This will not be a big deal for those players because they won't have to pay penalties and they will find real competition which can only be good for the game.
Even for the workload of the servers of the game it could be a good thing. Less leagues equals less races to load.