this is a misconception, “carcinization” doesn’t mean that literally everything eventually becomes a crab, people or dogs or sharks will not turn into crabs over the next hundred million years. it only applies to marine arthropods; things like lobsters, shrimp, and isopods have a strong tendency to fold their tails under their body, and get wider and flatter, becoming crab-like. the creature in the image, with its long straight tail, is more lobster-like than crab-like, and thus is actually a counterexample to carcinization