The design wasn't brand new, it was an extension of old technology which was extensively used and understood. It was nothing groundbreaking, just an up-scaled shuttle SRB.
My understanding of the motivation behind Ares was that there were people within NASA who felt that they should still be in the launch game, and Ares was their last gasp. They chose the SRB system because it was something they could design and contract out at a relatively low cost, and with the level of expertise they still had. The combination of inexpensive private launch companies like SpaceX, cost overruns, and political changes killed the program before they could make it successful.
Ares had problems for sure, but every new rocket system has failures. They would have made it work eventually, it was a matter of investment. NASA takes its direction from the US government, who told them to give up building their own launcher and use one of the many commercially available ones and to spend their time on more ground-breaking technologies and exploration missions.