I am not sure I entirely agree with the statement. I would concede that the Progressive Era sought to do more with its hopes and aspirations than prior movements, and because of this high level of aim, it might have given more reason to raise doubt. Yet, I think that it accomplished a great deal. In an America that was driven by economic and industrial success, the Progressive Era sought to bring more voices into the American discourse. These voices might have been silenced because they did not represent the wealthy or most powerful. Yet, it is because of the Progressive Era that the narratives of the poor, the working class, women, and individuals of color began to be heard and integrated into the dialogue of "what it means to be American."
In actuality there are two distinct Progressive Eras, one before 1901 during the Gilded Age, and one after, starting with the Presidency of Teddy Roosevelt.
The pre 1901 Progressive Era was quite unsuccessful, made up of suffragists, the temperance movement, novelists, socialists and others active against the abuses of the time. They were largely ignored and had very limited success.
After 1901, Progressives enjoyed quick successes under Teddy Roosevelt with the Meat Inspection Act, Pure Food and Drug Act, conservationism with National Parks, and labor reform under the Square Deal. There was also fairly aggressive breakups of large trusts during that time. By Wilson's presidency, progressive amendments were adopted to the Constitution.
So it really depends which Era you're referring to.
I would argue, for the most part, that the Progressive Era was not a failure. In some areas, it succeded and in others it paved the way for further progress later on.
I would say that the main success of the Progressive Era was political. The Progressives managed to get such changes as the direct election of Senators and suffrage for women. In many states of the West, they got things like initiatives, referendums and recalls.
In economic terms, there were successes as well. They managed to get government ownership of utilities in many areas of the West. The electricity I am using to type this comes from a government-owned utility. They also won a fair amount of government regulation of the economy (Pure Food and Drug Act, etc).