We cannot distinguish a project with only one sight, they are seems like same at glance.
Trying to search for warnings and red flags in the project is a good method to distinguish real from scam projects.
I guess we need to cost our time for the best outcome and participating in a good project.
ICO projects nowadays is just like gambling, a game of luck, you might be lucky enough to participate in a genuine one by chance, so many ways people use in detecting a very good projects, especially the new ones are no longer working, and this is why many people are falling back to the method you advised, which you method can only work for already existing projects, it is when a project is already existing and had investors that you will get review on it that could lead to giving it a pass or making it as spam with red flag.
I wouldnt say we should no longer invest in new ones but we have to be very slow in taken actions and watch carefully.