I've backed over a hundred projects on Kickstarter and have spoken with a lot of the people who run them. You don't have bad juju and I don't think they're giving unrealistic delivery dates. They're usually giving best case scenario dates. It's the optimism that needs to happen when they run a KS campaign that grips them. When they plot out their timelines they think it will be smoother than it actually is. So in their minds it's a realistic delivery date, but in practice it never was realistic to begin with. They're all just estimates anyway.
A good general rule if to add three months to each project even if they're a year out. The problem comes from the very nature of Kickstarter itself. On KS we're funding for items to be manufactured by people who usually have little to no experience in actually bringing a product to light. They don't anticipate the little delays that happen and add up. They learn as they go. You'll see some who have run many campaigns and funded many products still be late. Still, it's a lot better than it used to be hahaha. With playing cards it's often tuck boxes that cause delays for some reason.
I remember a project where the developer completely forgot about the month it takes for the sample to be approved. Had he remembered that bit, he would have been on time with his dates haha. Had one KS project I backed where the manufacturer shipped the entire run without the card embossing and had to rerun it. They received smooth instead of linen finish, that was funny. The delay wasn't, and I have no idea how their manufacturer didn't catch that, I think that's what made it so funny to me in the first place.

Other times they miss their estimated delivery date because they're adding more to the product as well. Occasionally someone will have so much success that they want to give the best product they can, so they go above and beyond the promised product. I've received one that was better than they promised and I'm waiting on another one that almost doubled what they promised. That's kind of nice and kind of irritating all at the same time.
Also a major problem is shipping. It's usually one or two guys shipping the product out once it's been manufactured and all that good stuff. They'll be regular human beings like us with jobs and all that, so while we want our items quickly. It takes them weeks instead of days to get the things in the post when they're not using a shipping service. Most don't due to the expense of a shipping service.
There are still the occasional scammers out there as well. Have to keep an eye out for them. Red flags are red flags, unknown manufacturers, stupid sounding price point, location changes, lack of communication. Things like that can give a good heads up on what's not going to be made. Can never be 100% sure though. On those projects, I don't pledge more than a few dollars. Usually less than the price of a blu ray.
tl;dr They're almost
ALWAYS late.