As a bishop, JP II was given opportunities to leave the country many times, when people couldn't leave unless they brought back important  information for the Party.  

JP II's experiences came from a church and nation cut off from Europe for most of the 20th Century.  His Church was the Baroque Polish Catholicism from the 1920's.  Baroque Catholicism is noted by focus on individualistic spirituality, by seeing the church as an extrinsic power suspended the divine and the human, and the Baroque church was "theater oriented" [which suited JP II just fine]---pilgrimages, emotionalism, visions, processions, benediction of the Blessed Sacrament.  The 'church' according to the Baroque period was the enclosed mystic, the distant missionary, the pope, and saints from the past.

JP II thought his experience of church was that of the entire church.  But he missed it.  Liberation theology is not Marxism.  In Poland, the documents of Vatican II weren't even published until the 1980's