I've been using nginx for years and switched to Caddy just because I was so fed up with configuring nginx to automatically renew TLS certs issued by Let's Encrypt. This is so much easier and reliable with Caddy.
I know about certbot and have considered it, but our customers can use their own custom domain name, which means we need to be able to select the certificate depending on the SNI hostname, which is a bit tricky in nginx. It's possible to use the $ssl_server_name variable in the ssl_certificate and ssl_certificate_key directives, but then the certificate will be loaded for each TLS handshake. And also need to be careful with race conditions when refreshing the certificate, to ensure that the certificate and they key are matching. Overall, it's doable, and people do it, but it's not as straightforward as just using Caddy.