Very important. A product is what determines if a coin will last long in the market or if it will die out. If there isn't a good product then people would not use it which affects the value of the coin.
Its one of the keys to the success of the projects, It would better to say it is the main key. If there is no product its just a new scam project with out any goals
This also. Without a good product, there is no way that a project can be successful. People will find out eventually that the project is useless and they will leave. The project will crash regardless.