My point was that "random deb" and/or "random web application" are way less likely to come with unsafe default ENV based configuration files and usually go with the config files securely stored in system directories with the proper permissions enforced during installation or simple .php config files that won't get exposed and that will require the user to configure in a proper way (like WordPress does by providing wp-config-sample.php but not the final wp-config.php file required to run it). Those are the solutions people used before the containerization hype and things were just fine.

My second point: containers "lowered the bar", allowing for almost anyone to be able to deploy complex solutions and this was / is bound to be a disaster. No matter how safe Docker and others become we can't just expect people who know almost nothing about computers and networking to be able to safely deploy things. Even the ones that know a lot, like developers, sometimes use Docker to deploy things they wouldn't be able to deploy otherwise and fall to the pitfalls of not understanding networking and computer security.

In any case, I would not expose such application outside of a VPN, which is a blanket security practice that most selhosters should do for most of their services…

Well, me too, however I understand that some people might want to expose it publicly because they might want to access their instances from public or work machines where they can't install a VPN. For those cases I would recommend 2FA and only allowing specific IP addresses or ranges access to the thing - the office static IP, their ISP or eventually only the user's country.