The scenario you gave was:
What about 24" MP, 2400 RPM - about 70% power on an IO-360 - at peak EGT as approved by the Lycoming manual.
I said that if you enriched the mixture to around 25C ROP, you could move to thrash or punish territory. It is certainly the worst place to set the mixture if you're interested in engine longevity.
This is exactly the range where engine manufacturers design the engine to be run. I don't understand this idea that aircraft engines are light, powerful, reliable, efficient, wonders of engineering and the designers are incompetent and don't know what they are doing.
It is indeed patently clear you don't understand. What's worse, you won't understand.
I pity the wallet of the poor bastard who owns the aircraft you fly.