>What if Netflix (or some other production company) produced a compelling show with an incredibly critical narrative about the PRC and its leadership?

In a way, they've already done this. See "Joshua: Teenager versus Superpower". It's a documentary from the precursor to these protests, the Umbrella Revolution of 2014. They definitely don't take a pro-PRC stance on the issue.

>Would citizens in mainland China be able to access it through roundabout means?

Yes, VPNs are very common (especially among younger and more educated populations)

>Would you be able to sow the seeds of democracy? Would they even be interested?

This is more complicated. It's important to realize that there's a rational reason that many people have for supporting the CCP. On the whole, their lives have gotten significantly better over the last couple of decades. They're optimistic about the future. Attacks on the Party are attacks on the mechanism that has ushered in economic growth. To this extent, I wouldn't expect democracy to be welcomed by the average person any time soon; it's simply not a national value for them in the way that it is for the United States.

(Huge caveat: remember it's a country of over a billion people and making generalizations is necessarily going to gloss over large sub-populations that may have an entirely different world view)

Its been a while for me too, I lived in Beijing for a little over 3 years and it has been my experience that access to western media was not all that difficult. There was a general consensus among my friends (mostly academics) that this was by design as the state saw a need for at-least some dissenting discussion among an "intellectual upperclass" to prevent stagnation. I find it amusing that the state controlled news media sounded more like an epic drama then anything we in the west would consider "political news".