But some rights are required for socialism to work as well. If you do away with seperation of powers and legal protection of basic democratic rights after using them for the revolution (which is what I mean by liberal institutions), then all that will happen is the leadership will then abuse their power, make themselves impossible to remove, and then restore capitalism to benefit themselves. This is exactly what happened over the 20th Century.
Even if you envision some form of Council Communism or syndicalism, you still need to have separation of powers to ensure that elections are overseen fairly, and you still need to legally protect the right to free speech and assembly otherwise there is nothing to stop people in power - even if elected - from repressing criticism and critics of themselves. So democratic norms are a good in and of themselves. You need to have them as a precondition for socialism to work otherwise you just repeat the 20th Century again. If it doesn't go through this stage, then democratic revolution must necessarily be a part of a socialist revolution.