NetNewsWire is getting a successor, Evergreen [0].
[0] https://twitter.com/brentsimmons/status/1020079742869884928
I'm not sure what ReadKit is missing, to be honest. It looks a little dated but you've got to be used to that if you're a NNW fan.
I wish ReadKit didn't seem abandoned. Great keyboard shortcuts, Pocket integration, and no attempts to algorithmically sort items. I wonder if this is another app that got hurt by the lack of upgrade pricing in the Mac App Store. I'd pay again if I could.