I agree that the success of IEO depends from the exchange, but a lot of depends from the projects itself and how useful is the platform of project.
Not everything depends from the exchange. On the exchange there are a lot of tokens and many tokens are not traded at all. Tokens must be in demand to be traded.
The platform of the project must be in demand and be used by people. If platform is in demand and people use the tokens the price of the tokens would grow.