The fundamental problem was unproductivity, which resulted in shortages of consumer goods and queuing for things such as sports shoes.
The system boasted enormous production of coal and steel, but was much worse in producing "less interesting" items such as "glue that worked", "washing machine that would not vibrate like hell" or even enough toilet paper. At one point, we had a shortage of sanitary towels.
Dissatisfaction with those elementary things contributed to the Velvet Revolution much more than lack of political freedoms. Plenty of people can live with their mouths shut, but they start getting really resentful if their new shoes leak.