I think right now Oculus is more focused on bringing VR to a wider market than they are on pushing specs. If you look at it from that perspective, the Rift S is a _massive_ improvement. No need to mess with sensors during setup; just plug and play.

And it's not like they've abandoned R&D into higher-end tech. It's just that resolution and FOV improvements are bottlenecked by modern GPUs. To overcome that bottleneck will require a breakthrough in foveated rendering technology; which Oculus is working on but hasn't achieved yet. (I believe Michael Abrash, the chief scientist at Oculus, estimated it'll take them another ~4 years to get the technology to the point where it's ready for mainstream consumer use.)