If Earth's axis had no tilt, we'd only have spring and fall for seasons, right? But which hemisphere would get the vernal equinox and which would get the autumnal?
The seasons are not caused by the earth being different distances from the sun: the earth's orbit is only slightly elliptical - it is essentially circular.
The seasons are caused be the axial tilt of the earth. So if there were no tilt, there would be only 1 season (or one might as well say no seasons).