Have we erected the prison if we've been made incapable of envisioning anything else?
You accept being a 'victim' (of circumstance), just by adopting that perspective.
Hard experiences in real life can knock that one out of you! (and crush many, also, along the way - nature and evolution cares nothing for illusions).
Imagination isn't the key (in my opinion).
Imagination comes after leaving the mind prison, not the key to set you free.
I can give you half a dozen examples of people on hive that are trapped in 'the mind prison' and don't even realize it - and yet they 'use their imaginations' to write posts.
It doesn't free them - it perpetuates the illusions.
The key, is - in my opinion - being able to distinguish reality from illusion.
'Pragmatic eyes', rather than 'dreamer eyes'....
And then dream away - it's fun!