nginx has been a fantastic project ever since its launch with little real competition out there.

That said, I've been running it since the early days, on super heavy production loads and never felt the need to have some more "decent" metrics out of it. I assume you're referring to real time metrics here.

Most if not everything can be gathered from the logs, which nginx is very flexible with.

I fail to understand why some missing metrics in a great product make you think to migrate everything to Caddy?