I will make the thought experiment simpler for you, can’t see you all struggle so much on that.
We can straight away discard the idea of constant speed of light using the same twin flight experiment. Imagine that a beam of light with velocity ‘C’ is shone towards the west. A west bound flight whose velocity is ‘0.2C’ will measure the velocity of light as only ‘0.8C’ unless its time gets dilated. Similarly the east bound flight with a velocity ‘0.2C’ will measure the speed of light as ‘1.2C’ unless its time runs faster. But we know that this was not the case from the above experiment.
I said just imagine.
Lack of simple imagination power is not a limitation (with reference to the crowd here)