I respectfully disagree about the league being a waste of time. The single tournament payouts are too low and the grind to get it is definitely not worth it. But if you are aiming for a top 15% place instead (even the cash prizes) and the points to qualify for a top league place then it's a different story.
ag77 already mentioned about the top 2K getting promoted. There are also cash prizes for the top 500 players in the league. Read more
here. The cash prizes also increase as you move up to higher leagues. Note: You will only receive the cash prizes and promotions to the higher leagues if you have atleast one lifetime deposit.
I played the elementary league in May and will be promoted to Masters next month. I play strict ABC poker (very tight and nitty in the beginning). I final tabled two tourneys in the elementary league (5th being my best placing). Racked up 1273.48 points for a 67th place in the league and a $4 bonus.
It is tough with so many donk shoves but you are allowed 52 games and the best 15 results. The odds are in your favour to do well and get promoted to HS. Good luck!