And there you have an example of what is going wrong. NR should only be liable if injury occurs during correct and careful use of the crossing (wrong side failure, for example). Anyone causing / suffering accident by their misuse of a crossing should not only be eligible for compensation but liable for all costs arising.
You're of course 100% entitled to your view, but surely you can accept that Network Rail have responsibility for all of their railway's "users" - and that that includes all staff, passengers and people crossing their land?
If Network Rail don't follow a set process such as a level crossing risk model, how could they show at Court, were it to come to a claim or charges against them, that they had fulfilled their duty to keep
all of these users safe? How can you rationalise knowing the risk of crossing misuse, but not intervening to mitigate that risk, when the lives and limbs of railway staff and passengers who are on trains are at risk, not only the users of crossings? It absolutely would not fly at Court that Network Rail had fulfilled their legal duty to keep railway users safe because they planned to recover the costs of compensation for anyone killed or injured owing to misuse of a level crossing from the person who was misusing it.
Network Rail could advance the defence at Court that they did everything possible to mitigate the risk of a collision arising from misuse of a crossing by preventing that misuse through measures such as automatic gates. In extremis therefore, Network Rail are obliged to close a crossing if the risk assessment indicates it can't operate within the tolerances and mitigation isn't in place. This does happen on occasion, for example, there's one such crossing in the Deganwy area. As Network Rail state time and again, no other interfaces present the kind of risk that crossings do, although obviously there is still lesser risk elsewhere, such as holes in the boundary fence, gates at access points not being secured and issues at stations.
As a thought experiment, suppose that you're exposed personally to dangerous doses of radiation, and lose your house and any possessions in it as a result of a radiation leak from a nuclear power station. The leak was caused by a criminal trespasser and attempted thief who broke in and tried to steal something, but in do doing caused a small amount of radiation to leak. Your house is part of an exclusion zone for decades as a result. From whom might you attempt to claim damages: the trespasser, or the operator of the nuclear power station?
A hypothetical Network Rail or nuclear power station operator in both of these cases would be able to bring claims against the trespassers, assuming that they were still alive, but such claims couldn't possibly hope to cover the cost of damage that might be caused. If the trespasser were killed in the course of their offence, likely nothing could be recovered at all from them.