If Microsoft made the same decisions as Apple did with the XP release (including always running apps in a sandbox), then yes, you wouldn't have to worry about malware at all on Windows. Instead, we have a billion dollar antivirus industry.
> Because of this, any device running iOS 12.1.4 is not only immune to these particular attacks, but it can’t be infected anymore either, due to the reboot when installing 12.1.4 (or later).
iOS certainly has malware and vulnerabilities, like any software, but they end up patched pretty quickly. It's definitely not the malware landscape we had on Windows 2000-2015 (arguably when Windows Defender got good).
