I got it to work, using the Google Calendar community plugin by YukiGasai, but it was, indeed, a monstrous setup process. 
Among other things, I had to pretend that I was a software developer (or something of the sortā¦), wrestle with Googleās console of some sortā¦ The setup was something like 39 steps, I think. Credit to the plugin author, because he provided such detailed step-by-step installation instructions in a PDF file, that I was able to follow them easily, even though I had no idea what I was doing. 
I ended up with a working Google Calendar plugin in Obsidian, but for now, maybe similarly to you, I have no idea how to accomplish in it the very thing I was setting it up for: the ability to pull ādue datesā from my Obsidian (I also use the Tasks community plugin by Martin Schenck & Clare Macrae here in Obsidian), and display them as events in my Google Calendar.
Iām currently lost, unsure whether this Google Calendar plugin can even accomplish that. If itās meant simply to display Googleās calendar within Obsidian ā well, I donāt really need that. 
I can always launch Google Calendar in a regular browser window via a keyboard shortcut, after all.
Iām a long-time Dynalist user, and Google Calendar integration in Dynalist (by the makers of Obsidian) works pretty smoothly, and is easy to set up. You basically push a single button, and thatās it. Iām surprised itās such a stupendous task here in Obsidian.
The Google Calendar integration in Dynalist is almost perfect: the only thing it canāt do, via Dynalist, is to set up notifications (pop-ups or emails). But the due-dates get transferred reliably from Dynalist to Google Calendar as events. Iād be very grateful if the Google Calendar plugin could accomplish the same thing here in Obsidian, but just like you, Iām currently lost as to whether it can do it at all, and if so, how. 