Economic Reformation completely transformed the government, causing it to be a shadow of its former self by killing millions of jobs at government owned companies. The party survived and subsequently thrived. Chinese unification is a centuries-old goal wholly unrelated to economic development.
I recommend reading Richard McGregor's The Party for a good introduction on the forces at play in modern China.
The party would serve no (meaningful) purpose if it lost it's ability to govern, so stability of government is equally important.