Firewall is pre-installed, and they offer to configure and enable it on launch (similar to Ubuntu and many other distros). I’ve never seen a Linux desktop they came with firewall preconfigured in any way.
The lock screen is an issue, and Cinnamon does not come with a Wayland way to lock yet. KDE, Gnome or some other Wayland friendly DE would be better in that regard, I agree
I think your first point is the main reason Ubuntu has its popularity to thank for; 10-15 years ago it was (one of) the best desktop Linux OSes, people used to its workflow will continue using it as there’s no imminent reason to switch to whatever new thing just came out