Airdrops aren't always waste of time, it depends on how good you are with them, the easiest way if detecting a good Airdrops is to watch the rating on top Airdrops platforms like airdropalert or airdropbob, if it's rated 5 starts it's probably because it's listed on coinmarketcap and it's trading
I never believed in sites like that. They work transparently and make false judgments, I have participated in a lot of airdrops from their website but as a result, no project has been really successful. And they never send tokens to my wallet