What I'm reading is not to use containers for a web server, which makes sense because web servers have had vhosts since forever and you can host any number of sites on there independently already

But what about other services, like if you want a database server as well, a mail server, etc.?

I started using containers when I last upgraded hardware and while it's not as beneficial as I had hoped, it's still an improvement to be able to clone one, do a test upgrade, and only then upgrade the original one, as well as being able to upgrade services one by one rather than committing to a huge project where you upgrade the host OS and everything has to come with to the new major version