Focus stealing has been an issue in windowed multi-tasking environments from the beginning. It's certainly been an issue in all macOS/OS X versions I've used since I started in 2011.
My latest version of the problem is with Ubuntu Gnome. Upgrade software and, later, you will be interrupted with a pop-up window to enter your system password. Not only is this an interruption, I’m always doubtful that this is the system asking for a sudoer password!
UIs, in my experience, are very bad at handling “interrupts”. Sorry, my dad designed chips, so I use that hardware term when talking about notifications and other times another application needs to notify or get the input from user. Personally, I’d have the UI change the color/texture of the system menubar/taskbar and wait for the user to click it.
Just install the SuperTyping app. It's sooo good and intuitive. Totally worth the $189, if you consider how often you need to type something.
I also recommend Little Snitch as firewall and Parallels for virtualization.
Does anyone have a recommendation for bootloader or filesystem app? Preferably subscription model for intuitive accounting.