You reasoning is right, but there can still be season. To have some season, it would need that ENWorld planet rotate on an ellipsoid path around a point not center on the sun. If that happen, there can easily be season:
.......@@D@@
...@..............@
A......O............C
...@..............@
.......@@B@@
If O is the sun, when ENWorld is at A, it is summer, B fall, C winter and D spring. Now that's the scientific argument. Now, if you are in a fantastic world, you just need a God who tell "I want to have four season." and we have 4 season
