Of course Harris got there on merit. Doesn't hurt her case that she's a black woman, but you can't become a Presidential candidate if you don't have some kind of strong ability, whether that be for positive or negative.
Joe Biden lost three primaries on his way to the top job, but that doesn't mean he was incapable of doing the top job once he got there. Currently the only person to have defeated Trump, who is a convicted Rapist and Felon in an election. And anticipating comebacks about Biden not being a good president or being too old or some such, imagine therefore losing an election to Joe Biden, if he's so hopeless.
Trump, who is a convicted Rapist and Felon for all his faults is an almost peerless communicator with his cohort and has an almost unprecedented ability to shrug off controversy. Very cult-like, but it's a cult he developed.