IMHO the "better" MacOS was the LisaOS, and came before the Mac. Cooperative multitasking, memory protection, task/object oriented user interface.
MacOS took much of the concepts, but was deliberately made "worse", so it could fit in the Mac's tiny ROMs, and not use an MMU. It was built as if it was a one-off with no serious consideration for the future (not an uncommon theme in the time, many companies hadn't really caught onto the "platform" concept yet).
(Re: the IIgs, building an elegant OS on the 65816 is annoying as hell with its banked memory architecture, tiny stack that can only be in the bottom 64k of RAM, poverty of registers, and lack of e.g. memory protection mechanisms. But the IIgs stuff was really a valiant effort, pretty cool.)
MacOS took much of the concepts, but was deliberately made "worse", so it could fit in the Mac's tiny ROMs, and not use an MMU. It was built as if it was a one-off with no serious consideration for the future (not an uncommon theme in the time, many companies hadn't really caught onto the "platform" concept yet).
(Re: the IIgs, building an elegant OS on the 65816 is annoying as hell with its banked memory architecture, tiny stack that can only be in the bottom 64k of RAM, poverty of registers, and lack of e.g. memory protection mechanisms. But the IIgs stuff was really a valiant effort, pretty cool.)