Speaking not as a train driver, but as a passenger and ex-railway employee, my view is that they are ridiculously bright (and show no signs of levelling-off). Light pollution is a wider issue and cheap LEDs now make it depressingly easy for everyone to have extreme lighting and pay no attention to the environmental cost. For trains, a fraction of the brightness of modern lamps would be adequate to see reflective signs and to be seen by track workers. It feeds on itself - brighter and brighter lights make people less aware of dimmer (but still perfectly adequate) ones and so the cycle escalates. Even with lights far brighter than current ones (God forbid) train drivers usually cannot stop in time if a hazard is illuminated.
As an aside, I think that road vehicle headlights should be banned in areas with street lighting, and just use marker/side lights, as drivers do not need them to see with, only to be seen. The huge level of light pollution could be cut greatly. Also, of all the types of transport, the railways are where headlight beams can/could be very accurately set to avoid dazzle, but they are not. I also speak here as an astrophotographer with the attendant dislike of light pollution.