"He's intelligent, but not experienced. His pattern indicates two-dimensional thinking."Also, today we have fire-and-forget weapons that can engage targets that are out of sight, yet in the 24th century they’ve gone back to close-quarter dog-fighting.
And despite space being 3D, spacecraft always move and meet in the same plane and in the same orientation.
View: https://www.youtube.com/watch?v=RbTUTNenvCY
That's the only time I can think of where the third axis was used tactically in combat. Even then it kept its orientation and slid "downwards".