I don't think the occasional piece of pizza crust is going to do any harm, but obviously don't overdo it. Dogs evolved as scavengers, and up until fairly recently they mostly got by on table scraps before someone had the brilliant idea of telling us we had to only feed "scientifically balanced" meals to our canine friends. Funny, it is acceptable to feed your children fast food garbage, but God forbid you should feed your pet anything that isn't "veterinarian approved" (most vets know diddly squat about nutrition…...they get a short course provided by guess who? The dog food companies!)
"People" food is fine, IMHO, but beware the known toxic items. Most people know about chocolate, but some aren't aware that raisins and grapes can be dangerous. My Basenjis have always loved most vegetables and fruits, and popcorn is also a favourite. But I feed a good quality dog food for convenience (NRG dehydrated) and supplement with veggies when I am cooking.