This is a genuinely interesting question - if humanity had the technological capacity to set the global temperature at any value, what value should that be? Is there any reason to think that the temperature in place from the beginning of the Holocene to the beginning of widespread fossil fuel usage by humans is the best one?
I agree! Intuitively i would think that most ecosystems evolved to adapt to their environment and, unless this environment is characterized by large swings in temperature and other conditions, will suffer in conditions different from the ones they evolved to thrive in. That means that any change in conditions needs to be slow enough for these ecosystems to gradually adjust by whatever means they have access to.
