> If trees needed to photosynthesise faster they would already be doing it.
You are anthropomorphizing nature. We human have needs, we modified crops and plants for bigger and tastier fruits and vegetables. Trees and nature doesn't have "needs". During the carboniferous, trees set the atmosphere on fire due to excess of dead trees (wood) and oxygen. They "didn't care". Hopefully, later, creatures evolved & processed trees and a balance was achieved.
OP's underlying argument is based on evolution and adaptation. They're anthropomorphizing as a means to easily convey their point, it is not the point in literal sense.
You are anthropomorphizing nature. We human have needs, we modified crops and plants for bigger and tastier fruits and vegetables. Trees and nature doesn't have "needs". During the carboniferous, trees set the atmosphere on fire due to excess of dead trees (wood) and oxygen. They "didn't care". Hopefully, later, creatures evolved & processed trees and a balance was achieved.