Hollywood makes us dumb. Here's the deal: Spock is a "Class M" planetary being. That means he breathes oxygen. As a mammal, he must have iron based blood, not copper based blood. But, if he did have copper based blood, the heat on Vulcan would kill him. You can't Roddenberry that.
The M in m class planet stands for Minshara not mammal
You assume 3 things above. Mammals exist on other planets. That blood must be based on a chemical make up we currently understand and have replicated. Vulcan is not that hot as its an M class planet.
We're talking about Spock. Spock is a mammal. A mammal with copper based blood would die on Earth. Vulcan has a warmer climate than Earth.
Nitpicking nitpickers so fun! Mammals from other planets. Ya right.
Your sci fi comes with a certain amount of handwaving. Blood chemistry is just one of the things that are not realistic about Spock. His hybrid parentage, for example, indicates a common ancestor or a papal dispensation.