Yes, "original sin" really is quite wimpy and disappointing compared to innate total depravity. But the Catholic Church had to have an excuse to "replace" the previously-existing G-d authored religion with something else. Total depravity implies the futility of all human action and effort. So they came up with something that fit their needs just right: man had fallen enough that the already existing G-d authored religion couldn't save him, but the new one would.
Given the choice between a Biblical and a post-Biblical moral code/ceremonial, I choose the Biblical.
Me too.
Although I know we would differ on our assessment of the Biblical.