That’s true if the right side is a flue, but with neither fire brick nor flue liner in evidence, I suspect it’s purely decorative – I’m interpreting OP’s text description to mean that we’re looking at one of two lined flues, and one of two unexpected void spaces he found when removing the cap. I don’t think the void is actually connected to anything, and instead is just decorative, but if I’m wrong and you’re correct, then yeah – there are more serious issues to deal with here
My high-school friend group adopted “it goes” from our French class (“Comment ça va?” “Ça va!”, roughly meaning “How goes it?” “It goes!” being the common neutral greeting taught in French classes) and I slightly resent it being described negatively here.