Soreness in moderation is a good thing.

Seriously, a little muscle soreness is good. It means you've taken the tissue a little beyond it's current capacity and that is a good way to stimulate growth. You're body will still respond to exercise even if you are not sore, but it might be a bit slower. If your muscles are so sore that you can barely move the next day, the longer recovery required to get over that workout might outweigh the benefits of pushing that hard. So what you want is a soreness that is kind of like a friendly reminder that you did something hard but not so sore that you have to change the way you move or your activity level.

That's the rule of thumb for power muscles, those are your big muscles that are prime movers like your delts, pecs, lats, glutes, quads, hams, calves.

Postural muscles are a different story. That includes the deep muscles of your core. If your deep core muscles get that same type of soreness, good for you. But if not, don't worry about whether or not you're working them enough, you'll still get good gains with consistent work. Those muscles are meant to function at a submaximal level and that's how they are wired to your nervous system. It's very hard to work them at a level that will cause delayed onset muscle soreness because of that hard wiring and it's not really necessary. In fact, if you try to do hard ballistic movements to work them that hard, your body will automatically switch to cheating with the prime movers because that's their job and you might not work those core muscles as much as you would think.