Core is the status quo and challengers to the status quo have neither met their burden of presentation nor their burden of persuasion in order to successfully change the status quo. That lack of success does not mean that they will not be successful in the future to make various changes to bitcoin.... If you want to call that democratic, then sure, it could be some form of democracy to attempt to persuade and to present evidence sufficient to persuade a change.. or even to bring computing power or some other leveraged asset (such as public opinion or bitcoin user opinion), and some assets carry more bargaining power than others. At this point, the most bargaining power seems to be with the miners and the software developers, and there seem to be various factors influencing them.... that causes the directed changes, including seg wit and whatever is going to come thereafter.
No one is required to convince core of anything and can veto any decision they make simply through inaction ... the easiest form of voting = 0 effort. People have to actively go out of their way and choose to use core. It would be trivial for core to create automatic updates with their software or push updates but they refuse to for the expressed reason that they don't want to impose their decisions upon the community... ultimately a user needs to manually upgrading = the vote.
The consensus process within core isn't perfect but generally is a process of meritocracy , consensus , and where the developers attempt to carry out the will of the economic majority and users if their is an overwhelming majority of support for an idea. This is indeed a conservative approach(which is a good thing with this type of open source project) and means that if an idea is contentious it has little hope of being pushed through.