As a “superbacker” (yes, I find that somewhat embarrassing), I’ve found that of the projects I’ve backed that have completed (or obviously never will):

~80% deliver roughly on time or late-but-I-sorta-expected-that

~20% are very late but the product was still cool

~2% were just fucked (scam-y, or lie-ridden, or poorly-communicated, or serious health issues overtaken; or some combo of those)

Overall I’m pretty happy with the results.