Seriously, anyone who disagrees with that ends up with even bigger problems, like getting hit by ransomware. You, not some developer or Linus Torvalds or anyone else, are responsible for your client and your data. If you put your server on the internet without securing it properly, you deserve to get owned. Your negligence ends up hurting other people.

Is that so hard to understand? You have to take security seriously. My point is that a firewall is the bare minimum you should be thinking about when setting up your server.