And we do. We don't use openresty (at least at the moment), we use a custom-built nginx that includes — among other things — the lua module. It's a great boon, but something things are still hard or impossible[1], and we don't use it for every request, opting for the location syntax, and all its flaws, for most.

[1]. Conditionally streaming an upload to a backend (i.e., if auth fails, don't stream) is impossible; nginx will buffer the entire request body, either in memory or on disk, and there is no way to change this behavior.