He certainly was a miserable failure as a Republican president, but I wouldn't necessarily call him a miserable failure, generally, as a president. Think about Jimmy Carter, if want you want miserable failure.
Bush was so remarkably inept as a communicator, he damaged the Republican brand in such a way that it will be felt for a generation. You have to go back to Nixon to find a comparable example. The fact of the matter is if it weren't for Carter's misery index, it may have been many more years before a Republican could have supplanted the memory of Nixon in the political zeitgeist of America.
The Bush family = the family that killed Reagan conservatism in America. “Thousand points of light,” “New World Order,” “Compassionate Conservatism”; all of these abominations were the product of the Bushes. I am somewhat guilty myself, as I voted for him twice. I will never again “settle” for a candidate. It’s real conservative or nothing, and that EXCLUDES all Bush family members. To (kind of) paraphrase Davy Crockett; “They can all go to hell - I’ll go home and clean my guns.”
Remember, it was Richard Gephardt in 2004 who first called GWB “a miserable failure.” Now he should be the expert on such claims.