Hi shampoo,
When using assets that we got from websites, we cannot expect that they are optimised for performance. In fact, they are usually not optimised. For this reason, it might be that we have to fix certain issues ourselves.
The more detailled colliders are, the less performant they are because Unity’s physics simulation has to calulate more. The more enemies we have, the less performant our game will become. If those enemies have complex colliders, that’s even worse.
As game developers, we often have to come to a compromise. In this game, we have to ask ourselves whether the player will benefit from super accurate collisions. The answer is usually “no” because nobody will take a ruler to check if the laser is off of pixel or two. As long as the game looks and feels accurate, that’s usually sufficient. As game developers, we fake a lot.
We could do the same for the star ship but since it’s just one game object and since the game is rather small, we probably will not notice any difference. With dozens if not hundreds of enemies in the scene, the difference will very likely be noticeable.
See also: