Admittedly mobile was a bit of an afterthought and I only tested it on 4 devices. What device are you using?
Probably not worth supporting. :) Adding new features and figuring out ways to keep people playing might be much more worth your time.
I was going to disagree because the same countries that really like web games are often the ones using older handsets, but Apple themselves say only 8% of handsets are on iOS < v10: https://developer.apple.com/support/app-store/
Good point about market share though, hadn't considered that.