You'll never get any two former Amiga enthusiasts to agree on what made the Amiga an Amiga, only that the nebulous whole made it what it is.
The truth of the matter is, if it waddles and quacks like a duck then it might as well be a duck. OS1.x-3.x, MOS, OS4, AROS. As for the hardware it's even more vague.
In the end, all that matters is, does it do what you want?