I’m using Reeder 3 and it’s actually quite good. The author updates it when it’s necessary but yeah, no new features are in the pipeline apparently.
We should all switch to subscriptions for apps that we use seriously, to avoid this exact problem.
My only complaint would be I’d prefer to use the native share sheet, not have to go through the Reeder one to get to the native one. But that’s not a huge problem. And I think Reeder may predate useful share sheets in iOS.
This happened a lot on High Sierra, and the Mojave beta has made it much worse (although that is to be expected).