Because there were too much of them in 2017. Good projects are already made, junk only left (except some, but they are rare). So, there are less chances to get even a soft cup. Thus ICOs will be less popular in 2018.
The ICO market has been so diluted that as you said it is hard for them to achieve their goals and hard for us as investors to make a good return. The ICO market will not fail in 2018 but it will almost certainly decrease in size which I only see as a good thing.