Quirks are somewhat related to DNA and blood. Quirks are also like a muscle in the human body; Overusing them can be strainful, Quirk can be trained to become more efficient, just like a muscle, and last, but not least, they have limits, and guess what also has limits? I'll give you a hint: A GODDAMN MUSCLE.
But, it's also about what the Quirk effects in question. In all honesty, even a random Quirk might be related to everything in the human body. Kai, with Overhaul, has been shown to turn straight-up blood into solid, non-organic bullets that can remove Quirks. This means that he could literally create bullets with different effects that are related to the quirk's ability. And, it's already been said that the quirk itself has full control over matter when reassembling something, whether it be organic or non-organic. And, this also may or may not be true, I'm not sure, but Kai could fuse himself with people by using Overhaul to disassemble himself and then reassemble the person's body, giving him control over their Quirk(s).
If Kai could do all of that, then I'm sure he would be able to remove someone's Quirk by disassembling and reassembling them to where the Quirk didn't even exist at all in the human body, or even in their DNA. In fact, you could probably make someone younger with this Quirk, or augment or decrease the power of a Quirk. Basically, the Quirk can disassemble something and reassemble matter in any form or shape, which is just OP as hell.