Airdrops are not entirely worthless, but the thing is that, majority of them are, and besides, airdrop methods, or should I say "dynamics" have changed completely, projects planning to distribute their tokens through airdrops no longer do so the traditional way that we all are familiar with, which is to fill a google form where we provide our wallet address, and boom, we get tokens directly to our wallet, no, no, this method is now obsolete, and any project still using this method is simply farming users email addresses and a scam.
Airdrops have gone the way of mobile mining, which is, you mine the cryptocurrency on your mobile phone, like what many of us did and stil do with pi network, Avive, core Dao, Renec to name but few.