They might not have had a market crash but without those reforms, the soviet union wouldn't be able to hold on to what they took half a century earlier. Not to mention there would be a good chance for the various parts of the union to revolt. It would be like a DPRK they are just objectively poor. Some parts might be more advanced but on a whole they would be behind, poorer, and more oppressed. The problem with a planned economy is just that an economy is too large to be planned. What Decisions about what advances come at the opportunity cost of other places. See Stalinist USSR which has Heavy industry out the waaazoo, but it was so god awful at consumer goods and one of the worst logistics systems known to man. More so, What did the heavy industry get them? a more affordable military-industrial complex? That is a sure recipe for disaster.
Either the USSR tries to reform, or it would have collapsed in a violent revolution eventually. oppression and poverty on that level cannot be sustained and the house of cards will fall apart.