Not sure how true this statement is in general, but it’s definitely not true of course for what the project described as the use case, eg your own side project/app, which you’d obviously not be able to “apt install.” Unless OP meant like the supporting hosting/proxy infra like Apache/nginx, which yeah, that’s what this project is trying to avoid/abstract for the user to have to deal with.

At the end of the day if you use this tool I guess all you’d need to worry about (given the tool is stable and works obviously) would be apt upgrades of the OS and even that you can automate, and then just figure out your reboot strategy. For me, I don’t even want to deal with that, so I happily use fly.