Investing in airdrops requires experience and proper research so that we can choose a good project. Because new projects are very prone to fraud, we must be aware of this. I never invest in airdrops because for me it's just a waste of time.
Investing in airdrop projects isn't similar with investing in common crypto projects. Sure, it requires knowledge because we need to take analysis or research on the projects. Moreover, it is new projects, it is not easy to gather information of the projects. But if you feel it mostly waste the time only, kindly avoid to invest in airdrop projects.
I prefer to focus on trading and becoming a holder of the top coins.
Good idea. It is a safe way to focus on trading and invest in top coins. You need to trade with recommended coins, so you have low risk of losing money. As long as they don't reach their peak prices, you can keep holding if their prices don't meet your targets.

Currently, airdrops are quite busy but there are many complaints about the small results in the distribution of rewards.
What makes airdrops busy? Do they give participants difficult tasks? I'm not following airdrops, I don't really know airdrops.
Regarding the complaints or problem on the reward distribution, it has happened many times. Sometimes, the project teams don't give participants proper rewards due to many factors. One of the factors is too many numbers of participants joining the airdrop program.