If the Earth were to be tilted 45 degrees then this would result in chaotic and extreme seasons, because of the 45 degrees tilt, summers will be very hot and Sun rays will come directly at Earth, resulting in very hot and dry summers in which it could result in the lack of water for crops. Winters will also be very harsh as the Sun would be hard to even see in the extremely cold winters. Global warming would increase because the ozone layer won’t be used to this much exposure to the sun in the summers.
Ultimately it would result in the extinction of many species and destroy crops.
This just goes to show how perfectly the Earth is is rotating. Just one change could cause mayhem.
I hope this helped and have a nice day : D