The secret ingredient in most BBQ sauces is mediocrity
I've gone on record about my feelings for mustard. I've yet to weigh in on vinegar, which is almost equally offensive to my dainty palate. In Texas, where I proudly reside, we're more tomato-based, but ketchup soup isn't exactly something to celebrate, either.
You can dress up all these core components with fat and butter and oil and molasses and a handful of spices that you're great-grandfather wrote on a scroll and hid under a national monument, but when it comes down to it, there's no amount of complexity that makes these things worthwhile. You might have a beautiful pair of curtains, but if they obscure your view of the outside world, well, it doesn't matter how well they match the carpet (which, in this specific instance, is made of beef).