The fifteenth amendment was originally a failure because it was interpreted so narrowly as to essentially block black people from voting. Requirements such as poll taxes and literacy tests essentially blocked people of color from voting, so even though there was an amendment, it was not executed in such a way as to really grant these rights to the people it was intended to help.
Based on its history it is easy to say that the fifteenth amendment was originally a failure. The amendment was widely overlooked far beyond its passing. I think the federal government should have done more to uphold this amendment in its earlier years. I think this offers proof that some laws simply aren't followed which is something we should consider in the future.
The 15th amendment was a success in that it took away the racial segregation from voting. However, it wasn't implemented and at the time the United States government had no way of truly enforcing it. Also states at the time had different ways of suppressing the African American vote by other means that the 15th amendment did not address such as poll tax and literacy tests.
No, it could not be said that the 15th Amendment was originally a failure, because it was the first step in the right direction. People had to warm up to the idea. Other laws that are passing now, such as gay marriage and marijuana, are met with opposition, because people are not used to them yet.