Well i have tried the COSS ICO bounty recently but i was a total waste got paid close to 10USD after 2 months 
The only opportunity to earn on bounties is to participate in 50 to 60 bounties at the same time. This is a full-time job. Only this way you can earn money. Many bounties are not paid for this need to be prepared. If you participate in one bounty be ready, that wasted time in vain.I'm not agree with you. If you choose projects more carefully and don't take everything, you will be able to earn even more and at the same time not clog your accounts and not help spammers!