Modern OS?

[NorthWay]

"Modern" is a bad choice of words. It means one thing for an OS researcher, and another for an enthusiast.

Exec was designed for 128K, 7MHz, and a floppydrive. At that time OS design had included proper management of all system resources for 20-odd years already. Hi-Toro just didn't have the resources available for making it happen.

If you have gigabytes memory, gigahertz processor, and terrabytes storage, you have an expectancy of having all aspects of resource management in place.

Whatever "modern" is, it will at least include what was considered good practice 45-50 years ago. That includes MP, resource tracking, swapping/paging, address virtualization.
Note that none of this means you have to have a traditional unix style fork+exec regime where all processes start from the same address and basically share nothing.

What is ironic in all this is that the Amiga gave the end user many tools and options that felt very fresh and very friendly. Things that you'd think a modern OS could do.

What _is_ modern, and what _feels_ modern is easily not the same.

[NorthWay]

the lack of memory protection is baked into the way messages are passed between applications. Passing memory pointers between processes was a conscious decision to make it run quicker.

Sharing does not mean not protecting. I recommend checking out research around "SASOS" to see ideas about this. It has become quieter in recent times as it saw interest bloom when 64bit address spaces became commonplace.
The same ideas could have been applied to a 32bit address space when 128K was considered adequate (well, in many ways that is what Exec did, only with non-virtualized addresses, which limits your posibilities).

[NorthWay]

Let me try to list a few features I think of as "modern"

- support for hw acceleration of tasks AND using it: a display system knowing and using 3D or other accelerated features, an audio system able to offload effects to hw.

- an integrated object model: what enables you to insert a spreadsheet in your Word document

- a unified storage view: think volume manager or ZFS

- a failsafe storage system: (typically) a journaled filesystem

The last one might not be very modern. And yes, we have that.
For gfx we have 2d help, but the OS has no notion of 3D.
The closest to an object model is datatypes? (not close at all). Not that they aren't a brilliant idea (BeOS is the only other one to pick up that?).