Does This Debunk the "Coolant Can Flow Through the Radiator Too Fast" Idea???

People always ask, why does my old car run hot???? How many times is because the engine block was full of rust and c*** and thus all that got into the radiator.

Whats wrong with my car. Runs like c***. Ever clean the gas tank and filter and thus carb??
I’m afraid this might be an issue with mine. I’m on my second time flushing with garden hose before installing the new rad. I flush but it will sit a week (making more rust) while waiting for parts. I’ll flush again and hook it up. See where I’m at.