I totally agree with you that there is an easy to spot scam project and there is a really hard to spot projects but my own experience you can always find a hint that the project is a scam no matter how well played it is, in some situation I saw there was a really good looking ICO that is promising a lot of investors, they had perfect whitepaper, perfect site, and even a good team. But there was always some questions asked without any answers, and people just decided to invest and ignored the unanswered questions, these unanswered questions was the hint that people chosen to ignore.
You know "there is no a perfect crime" there must be a mistake somewhere.