It is possible to change the position of any vertex in a mesh, but the challenge is to make this modification work the way you want, You have to decide which vertices should be moved, when and what is the offset for each vertex?
Vertices are referenced by index too, so it is extremely hard to manually animate a mesh using code, using vertex shaders is easier but still not suited for animating car crashes quickly.
Skeletons are more straightforward because you can have poses that are set interactively and blend between them in a variety of ways, then finally play the deforming animations when your cars crash using code.