The speed of light ray (in vacuum) is always 100%. Other things keep changing in a way that keeps the speed of light constant from everyone's perspective.
So the fact that you always see light at speed of light whatever is the frame, isnt because light is going at speed of light but because light is light. What's different between a photon and my spaceship is not so much that my spaceship cant reach a full 100% speed of light, but that youll always see a photon at speed of light because of some "magic" property which cause isnt speed. Is that correct?
It is speed, the speed of light. Particles that have zero mass go at the speed of light. This is a property of the particle. That there is a maximum speed is a property of spacetime however. Even if there were no massless particles we could still discover special relativity, for example by noticing that when you speed up particles they can't get past a particular speed. In the large hadron collider they can speed up particles to 99.9999991% of the speed of light.
