I always find this a weird selling point, TBH.
It's probably a selling point for people who don't already know the existing $FOO.
For me, putting effort into learning the new thing only to use it exactly as the old thing is wasted effort.
I don't know what I gain by moving to the new $FOO, usually.
I would wager the vast majority of Nginx "installs" are running in a container now a days.
The distro doesnt matter and few are provisioning an instance of anything, that's some container orchestration job.
Last week trying to coax nginx to be able to set a CSP nonce in a web apps index.html which apparently meant I would need to custom build Nginx or a custom build a container with a custom built Nginx to install a plug-in to do it. This type of stuff adds up and having a bunch of stuff hidden in Nginx Plus doesn't help either.
I think Nginx is a great piece of software its just that people don't need all its offerings, they just want to host some tiny js and proxy to an API and things like caddy were built for that. The limited throughput doesnt matter when CloudFlare or Cloud front cache most of the things it is serving anyway.
As for the CSP nonce, I'm surprised that there isn't a plugin, but compiling isn't a big deal, just annoying. Alternately NGINX is scriptable or you can do it at the application level as well. If caddy is easier for you or for that use case, then that's great, use it with my blessing.