Not even leagues necessarily, just double ups really.
For example I just ran an optimal generated lineup for the hell of it tonight and I finished with 266 and 123rd. It cashed all the way down to 800th. Just throw $50-$100 in that every night and let it stack up.
In football I would just play the giant $25 double up and there wasn't one single week that I didn't cash in it. Just submit the same lineup multiple times or make 1 adjustment. Build your bankroll and then you can enter the big entry fees.
I guess what I'm getting at is DFS isn't broken with money flowing to the top, you just gotta go outside the norm. Sure it's not a 50k payout immediately but it really adds up.
If someone started with $25 for example at the beginning of NFL season and doubled every week and risked their entire bankroll every week they'd finish the season with 1.6 million and that's not counting playoffs