Airdrops are good and the truth is they have their good and bad sides. The airdrops you listed above are good airdrops as they paid from byteball ABBC coin, and steem engine airdrop. This airdrops were one of the best airdrops. I will loke to highlight a few things you wrote here and look into them one after the other.

So here i am gonna talk about airdrops that gave me profit and you might know about these aridrops. I have earned very good money from these airdrops.

A lot of people earned really well with airdrops starting from late 2016 to 2017 woth bitcointalk and ethereum introducing contracts, (if you started airdrop early, you could witness this) so i can say that this is true but also, a lot of people haven't really made much especially those who started airdrops with ethereum contract in 2018. Other blockchain paid like byteball in 2018 did well, EOS in late 2018 and 2019 gave a lot of project an easy listing with newdex so people made money from airdrops. Tron gave a lot of project owners who had tokens the Avenue to list easily and so airdrops were profitable but some airdrops were not profitable mostly those on ethereum.

First you need to read whitepaper and roadmap and also see what products or service they are providing.

From my findings, most scam or failed projects have the best whitepaper. Most project do not Intentionally fail, some do due to failed ICO or government restrictions.

After that check the registered license is ok or not. After checking all these stuffs. Go to the team section and check every team member's social media profile in detail and know the history of that team member

Even a scam project will take their time to organize this. More so, the fact that most people love decentralization, they often fall for projects without owners which claims to be based on decentralization.