Political Parties do one thing better than anything else. That is get people elected to office. They are needed for that, and to accomplish anything political ultimately that power is needed.
They are not the best movers of political change. The first being that most people are risk adverse and long standing political parties are very risk adverse. They have people who don’t want to lose the power and standing within the party. They are driven by a structure that rewards long term involvement, that rewards the same old, same old.
Women getting the vote, not led by political parties. Look at Obama and Clinton and see how they were followers not leaders on LGBT. The Civil Rights movement was not led by a political party. The Democrats followed dragging southern racists along with them till they switched.
Organizations are important. And like minded organizations can band together and support each other to move a political party. At this point the party itself can play a synthesizing tool. This is when and where real change happens. But parties are the last step, not the first. The fires have to be lit elsewhere so that the feet of the parties can be held to them.