Some might criticize the decision to be macOS-only, but as with most decisions, there are tradeoffs. Focusing on the Apple ecosystem allows NetNewsWire to feel like a native app (because it is)! Like other well-run open source communities, there is a clear Contributor’s Guide and Code of Conduct. It supports syncing with a Feedbin account, but can also be used with purely local subscriptions.
I use NetNewsWire every day on both my MacBook Pro and my iPad, and it’s so easy to use I sometimes forget that it’s even there. Without great clients for RSS feeds, consuming them would be more work and make it easier to default to algorithmically-generated, attention-stealing feeds.