Don't worry they are in every league at the moment. I remember the days where the bots were all stuck in silver and once reaching gold again the bots were gone and playing also seemed easier at that point.
Now they feel like they are in all leagues, and I really have issues with levelling up the leagues honestly which kind of sucks. I used to be a gold/diamond playing player and now more than often stuck in silver (or my skills started sucking as well...def an option :D)
But indeed...when all bots are gone, I doon't believe it would be good for the game as well, but a middle way should be good. Good for investors, good for players...but what that is? surely don't know :(
I don't know what the solution is either, as there aren't enough human players at the moment, but perhaps buffing the bots a little would handicap them enough :)