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To make it clear, what @Luuklag means is that the only way to use Stack Exchange properly is via a browser: if on mobile device, you can use any browser app, personally I recommend to install Chrome app and use it.
No the app is long dead, and there are no signs of that ever Changing. I find the responsive site perfectly useable. You can click "enable responsiveness" in the footer of the site, after you clicked view desktop site.
Then it needs to be removed from the relevant stores. New questions will continue to appear here about it (especially if the app advises it) otherwise.
Make sure to click the "full site" link in the footer if you are on the site on a mobile device. The full site is responsive and will replace both the mobile app and mobile theme and it has the same features (if not more) as the app.