Physics hasn't, but technology has. Coolant has changed, radiator pressures have changed, fuel has changed, tuning has changed (EFI and computer controls), the list goes on and on.
NASCAR's run "coolant" temperatures at ~300°F, are they trying to reduce their carbon footprint?
A factory 6.4 L hemi runs a 203°F thermostat, and that engine makes as much or more hp than what a lot of folks have in their classics and it will do 100k+ miles no problem.
It absolutely matters how your engine is being used, how it's set up, and how it's tuned. Saying "210°F is too hot for making power" is just silly. Yeah, maybe for a Pro-stock car, but not for a NASCAR or a factory 6.4.
Bottom line is on a street car 210-215°F is nothing to worry about as long as it can maintain it.
