Pan-democrats living in la-la land
I don't know of any successful democracy that does not have party politics, and the electoral rules and laws that sustain it on a constitutional basis. In his classic Democracy and Totalitarianism, the French political sociologist Raymond Aron goes so far on the importance of political parties that he uses them to define the two political systems: one system enables multiple competitive parties; the other only allows one dominant party that monopolises the state and military.
In Hong Kong, we have many political parties but very primitive party politics. The Chief Executive Election Ordinance even bars the top leader from being a member of any party, exactly the opposite of how it's done in practically all functioning democracies. In the fight over universal suffrage, the pan-democrats are going out of their way to discourage the development of party politics as much as the pro-Beijing side. Of course Beijing would do that, since by Aron's definition, a dictatorship would ban multiple parties, or at least those with the potential to compete for power, even if it's just in an SAR. But the pan-democrats? That seems self-defeating.
Beijing wants the nominating committee to be composed entirely of people from four sectors - business, professional, political, and a social and labour group. The emphasis is not on political parties, but at least there is a role for representatives from various political groupings.
Open public nomination, which the pan-dems propose, would simply undermine the ability of established political parties to field competitive candidates. This is because they place themselves on an equal footing with other groupings that could put forward as many candidates as any existing party. How ironic or noble that, in their fight for an idealised universal suffrage, they pre-empt the development of party politics that would benefit their cause? If they were more responsible, the pan-dems ought to give up public nomination, a non-starter, and fight for the widest possible party representation in the nominating committee to minimise or nullify the other three sectors, which are likely to replicate the corrupt functional constituencies. But in the la-la land of pan-democratic amateurs led by children, Beijing is the only pro in town.