Hi,
How would I go about making spaceship like movement without rigidbody 2D?
Not to just move player but also AI, and mostly AI spaceships has to behave like in space.
Because the rigidobdy2D is taking 50% of my processing power when I have a lot of objects on the scene.
You can try that with the classic high-school physics approach, although if the built in physics engine is chocking, i doubt replacing all rigidbodies will be an easy fix.
Give the objects a Vector2 speed; and float weight. Modify speed based on force-vectors derived from player input, taking into consideration the weight (speed += force / weight) and move each object in Update() by speed*Time.deltaTime.