The issue isn't describing what I see on Android. It's chopped off on the left and I can't zoom out. Not usable at all. As mentioned elsewhere, forcing the desktop view is better.
No, it's presentation software that's implemented via a website. The primary user of this software is the person giving the talk, not people on the internet. The fact that people on the internet can also see it is a bonus that comes with the choice of the implementation.
Complaining that this doesn't work on mobile is like complaining Powerpoint doesn't work on mobile.
Also, it is an issue: https://github.com/golang/go/issues/27026. Marked as "help wanted".