The issue was never that it'd stop working completely. Instead, the API would limit the app once a certain number of requests happened, and charge for more. Since a lot of people use the app, there's a lot of requests, and it stops working quickly unless the developer pays.

Now that the app has been pulled from the market and it broke for everyone, it sees very little use. The limit doesn't get hit, and the app works. But if everyone starts using it again, it'll break again.

Edit: Just for kicks, I downloaded it from apkmirror and tried it. I very quickly got the 429 error when the API key has hit the limit.

Reddit broke the API and blocked everything with the user agent containing "Android". Even their own app didn't work on some Android phones, including mine. Couldn't load anything from the official app.

It never stopped working for me, besides the outage the other day. I'm guessing it's because I'm a mod for a sub. They said from the beginning that they wouldn't break things for mods, and surprisingly, it seems that they've kept their word on that.