Nginx has been the best routing and traffic serving system for a while now, but it's showing its age. In addition to hiding metrics, HTTP 2 support is difficult, there's no clear path to grpc, and (as mentioned in tfa) there is no way to get stats out of it.
Envoy (envoyproxy.github.io) seems like the next thing. Nginx won because of the predominant patterns at the time, and it's still totally fine for serving lots of HTTP traffic. The problem is that if you're thinking microservices or rely on metrics to do your job or have elastic infrastructure, Envoy's feature set is the only real way to handle traffic routing in that world.
Disclaimer: I work for turbinelabs.io, and we're moving from nginx to Envoy to take advantage of a lot of these features to power our product. We've put a lot of effort into that decision, and believe it's the right one.