You're almost there!
Why do you think that a government will oppose a complete system change, but will allow a party change? You're a pol-sci student, you can get this one!
If a government had two socialist parties, would that make it more democratic and less authoritarian? But if both parties had the same goals, what would even be the point of having two of them? Would it actually be more democratic to have two parties, or would that just be a means of enabling the people to feel like things are more democratic, because they get to vote between two parties (but both parties ultimately have the same goals.)
Now imagine say...a capitalist country that does that. That has two parties, but both parties represent the capitalist class, not the people in general. Is that actually democratic? The people get to choose after all! But they only get a choice between two parties that don't actually represent them.
What is a democracy if not a government built around the representation of the people? If the people are feeling represented by their government, does it matter how many parties their are? More parties doesn't mean more democratic. What matters is that those parties represent the people. Even if there is just a single party, as long as the people have proper representation, it is democratic.