I'm not a native English speaker and I see a sort of striking contradiction in the use of the expression in the passive voice
something can/can not be + past participle
the problem can not be solved
I can't be killed
the door can be opened
I know what the English native speakers want to say with this expresion but I see it weird to attribute "can" to an object ; then "can" and the passive voice are contradictory – isn't it like saying :
the door can undergo to be opened
Can is bound to all what relates to ability,action…while the passive voice is bound to the passivity,non action…thus the expression is like
the door is active to be passive
1)"can" and "undergo" does not go together !
2)It's human that can,not objects (such as "doors") or abstract things (such as "problems")
I know ,maybe, I have not well explained my idea – but is this a legacy from an old language or just an habit that became a rule ?