I agree that the DeFi idea is the next generation of the ICO.
And were ICOs very profitable for the investors? 
Yes they were profitable for the teams who owned the project and the advisors, under-the-table private investors and so on. They managed to dump their shitcoin on the investors and silently exit the scene without saying a word and thus running a very nasty scam. It was a bubble and many people good fooled into investing in a number of ICOs, some used to say that they invest 100$ in every upcoming ICO - essentially a gamble.
Same is happening with DeFi. There were projects like BitRefill which are legit but not these hundreds of lending and stablecoins.
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but there are unique ideas of projects in the DeFi sector. I believe that some of the DeFi projects will become the next era of blockchain tech.
Yeah same as what the ICO buzz made people think. Keep dreaming before the reality is visible.