It is common sense to most people that democracy and dictatorship are completely opposed to each other. Dictatorship is bad because it excludes the population from political life and concentrates all power in the hands of a despot.
Democracy is good because it makes political power accountable to the people.
Marxist make a distinction between forms of government and the class nature of the state. Every state in history has been an instrument in coercion, by which one class enforces respect for its property and secures it rule against resistance and revolt. But however preferable this may be to a military of fascist dictatorship, methods and structures are built into this system to ensure that the working class can never use it to take wealth and property from the exploiters. MPs can make fine promises during elections, which they are then free to break, with no way for their electors to recall or replace them. An unelected House of Lords can delay and obstruct legislation.