I’m not too nostalgic for an OS that only had cooperative scheduling. I don’t miss the days of Conflict Catcher, or having to order my extensions correctly. Illegal instruction? Program accessed a dangling pointer? Bomb message held up your own computer and you had to restart (unless you had a non-stock debugger attached and can run ExitToShell, but no promises there.)
It had major flaws for sure, but also some excellent concepts that I wish could've found a way to survive through to the modern day. Modern operating systems may be stable and secure, but they're also far more complex, inflexible, generic, and inaccessible and don't empower users to anywhere near the extent they could.