If you're getting added to random groups then that isn't a bounty group, if not airdrop then I guess it to be Ponzi scheme. Bounties are well managed by BM, and they don't beg people to join their respective group not to even talk of them adding people randomly. To answer your question, yes, bounties still pays, you just need to be careful in selecting.
You are right, nobody will add you to bounty group, you will have to add yourself to it if you want to participate in bounty campaigns, if you are added to any airdrop group, know that the airdrop group is scam, nobody will add you to any original airdrop group, when you are added to any group, you have to be very careful, don’t connect your wallet to any of the link they drop on the group, or don’t even click on the link which they drop on the group, it might compromise your wallet address.