Ironically, I'm writing this answer from the app.
I am dismayed by this decision, and per comments, the further decision to shutter all SE apps. I don't see a single comment from SE saying that a new app is being developed, etc. Just some comments on how the app is apparently used so much, that some older code is bogging the system down. (Can someone at SE not simply ask how to make app requests more efficient? If only there was a site for that...)
There are enough users using the app that it drains some resources, and SE's response is not to fix or make the app better, but just abandon it and its users? I am curious, of those users who post/interact with the app, what percentage is via the app vs. browser? I trust someone did that basic research before shutting the app all down, so I would like to know.
For a site ranked #137 in global engagement according to Alexa (take that for what you will), this is a very surprising move in my opinion. I don't think the devs/executives at SE need to be told how popular apps are for customer engagement, branding, etc.
The fact that a website that is trying to be the primary place to find your programming answers (and other topics, on the broader SE network) for everyone, is shutting down their app tells me a lot. This coupled with the recent internal goings-on/firings/resignations sounds like a death-knell for the site's more active users, or even folks who are interested but don't want their browser to have to maintain a login/cookies on their cell phone.
I keep seeing that the app was killed due to relatively small user base. Again, apps are quite the popular way to interact with websites/companies — why kill the app, instead of actually taking initiative to make it better so more people do use it? Perhaps people installed it, without knowing it's no longer being maintained, and uninstalled assuming the company can't even make a decent app?
Also, Stack Exchange did a terrible job announcing this to the community. The very first sentence in the OP links to an Answer to a Question. This is where highly important information for users is given? Hoping that we click all questions on Meta for any site wide updates? And then sometimes get a little defensive about the app, and tell us that this has been announced previously? I feel very disrespected. Looking at the question alone linked to in OP, they did their good due diligence and browsed for an answer and couldn't find a simple announcement from the company officially stating their position on the app.
As of 28 Dec 2022, the app is just crashing now after a few seconds.
1/27/23 - As this is still getting some attention, I also want to ask how is actually using the site on mobile? SE's response to nuking the app was "The Mobile version of the site is fully functional, and just use that". While this is technically correct, from my Samsung Galaxy, when I visit SE.com, it's literally the desktop version (despite my browser not having "View Desktop Page" ticked). So, to log in, I have to pinch/zoom, scroll around, log in, then to browse the site, lots of pinching/zooming in (so I don't mis-tap/click). This isn't very ...mobile friendly. There are tons of "Make a website 101" courses that include how to "dumb down" the page for mobile (and as a reminder, mobile phones tend to have much smaller screens than even the smallest desktop computer). Why is the site, explicitly intended for mobile use, so frustrating to use? It's not even a simplified site that allows quick and easy use on mobile - I won't even get in to the frustration of formatting any answers on the phone, with the "full site".