I agree that the lower coefficient of friction of steel on steel leads to less favorable maximum speeds for trains when applying the otherwise uncontroversial standard of possibly needing to stop at an uncontrolled crossing. I don't see what the amount of mass has to do with anything though. Like we don't condone SUVs or tractor-trailers ignoring red lights just because they're heavier.

I'd say the problem with simply saying that uncontrolled railway crossings should be banned is that railroads will understandably say that it will take time to comply, and then stonewall for decades because of funding/whatever. Whereas the standard of liability can be changed atomically after some notice period, and if the railroads haven't upgraded their crossings to be able to maintain the speeds they'd like, that's on them.

Also the framing is different - actively outlawing certain types of crossings is adding government regulation, while eliminating the liability shield is an elimination of corruption.