I believe that Evangelical Christianity is indeed irrelevant in today's society simply because it refuses to evolve with the times. No one wants or needs to believe any longer that there is an amorphous diety in the sky that is judging and watching their every move, ready to rain down punishment from the sky.
Evangalist congregations are fewer these days than in past years. The revival of the church through celebration of ones faith was a hearty trend that entertained, enthralled and possibly saved many worshippers. That is all based on individual experiences. Today, modern technology, science, and technological advancements are bringing new ideas directly into your house. No need to read the paper or go to the library. There is endless knowledge on the internet with more being created each day. Facebook now has a larger congregation than any church in history.
I do believe that Evangelical Christianity is irrelevant in today's scientific and secular humanist society. People have enough knowledge and resources to find the truth they are seeking. People do not need people to preach the Gospel to them, because if they want that information, it is widely available to them.
Yes, Evangelical Christianity has no place in the modern scientific world. This form of religion teaches an extreme degree of ignorance and lacks the educational backing to enrich the lives of its followers. Furthermore, the public programs supported by these institutions serve to harm American institutions and legal systems, such as separation of church and state, right to choice, birth control and public assistance.
Christianity, even evangelical Christianity, is an important part of life for a large number of people. It is not necessarily incompatible with a scientific, secular lifestyle as long as you are able to find a balance in your life. While it isn't the answer for everyone, for others it is an essential part of their identity.