I'd say a good amount of reddit users use their mobile browser rather than us the app because the app is terrible. So to me, the answer is yes.
I use the app. It's fine for reading comments -- which is most of the reddit experience.
Use the website just as a middle finger to reddit for constantly pestering me to use their app. The web still works fine thank you.
I use relay and it's awesome, no ads and just better than their own app.
They are making the mobile website terrible on purpose so people would get the app
I use the mobile browser versions of Twitter, Facebook, and Reddit. I dropped the apps a long time ago. So yeah, one can easily survive without the app stores.
I doubt it. A small number of developers and enthusiasts might use the mobile versions, but most people won't. Google and Apple are currently gatekeepers and they're apparently cooperating.