[mmooss]

> IIRC it didn't take that long to develop first production versions of macOS?

If you mean the early 1980s OS, that is not comparable. It probably ran in something like 512K of memory off of a 5.25" floppy disk (or a tape?).

> It's not like Fuschia was supposed to be a "fully capable OS developed from scratch", either? I mean it's "just" the kernel and other low level components

I don't know the answer, but doesn't the second sentence describe Linux?

[fredoralive]

The original Mac has 128kB RAM, a 64kB ROM with a fair chunk of the OS in it, and used 400kb single sided 3.5" discs. The paltry RAM is generally considered to be the main problem, but the Mac team were working to a target price of $1500 (which they missed), and that’s all that could afford, with the largish ROM being a compensation. A quick unscientific look at Byte's January 1984 issue seems to show 128kB as the base level for IBM PC clones at the time as well, but they don't have a GUI.

In comparison, the Lisa OS required 1MB RAM and a 5MB hard disc, hence the eye watering $10,000 introductory price.

Development on the Mac apparently started in 1979, and release in 1984 although the early Jeff Raskin era machine was quite different to the final Steve Jobs led product.