When a program goes down on amiga os, it takes the whole os with all the other programs down requiring a restart, generally. Same for windows 95/98. Whats the point of multitasking when you lose all your work in progress because one of the tasks goes bad? Windows 2000 was a revalation, crappy software went down and the os just cleaned itself up and carried on. Uptime for a workstation went from days (if lucky) to months. From a productivity point of view, this was golden.
Also, security was not any sort of consideration for amiga os. I dont think I'd do my internet banking on it.
So I think that is the biggest difference between amiga os and modern os. Why this design was abandoned. Amiga is basically a toy computer. Great for people who wanted a toy computer. I'm glad i never had to rely on one for a living.
Raspberry pi 2 is so amazing because you get a proper, modern, secure, usable computer for 25 pounds. You get a lot of fun for your money, just like the amiga back in the day.