The failings of Reconstruction are not trivial.
They were to most white folk in the North.
Keep in mind that the North's objective in the ACW was to restore the
Union. Emancipation was a
means toward that end,
not (save for a few abolitionists) an end in itself. After all, as late as Nov 1864, 45% of
Northerners voted for a party whose platform called for a restoration of the Union with slavery preserved. And quite a few even of those who rejected it and voted for Lincoln did so not from any principled objection, but because they suspected (correctly) that it simply wouldn't work - that the Rebs wouldn't accept reunion until compelled by military defeat, no matter what terms they were offered.
Given this attitude, and the speed with which it became clear that the South really
had accepted reunion, and wouldn't try secession again in any foreseeable future, the remarkable thing is not that Radical Reconstruction failed, but that it achieved even as much as it did. If the South was reconciled to reunion, then promoting Black rights simply wasn't worth the effort. Note that it wasn't just Rutherford B Hayes and his immediate successors who thought this way. It would be three whole
generations before anyone gave the issue any further thought - because that was how long it took before they would have any
incentive to do so.