Why were the Aboriginals so primitive

I know that "primitive" is very subjective but bluntly speaking, why were they so simple compared to other people around the world. The only explanation I've ever been given was isolation. However there have been many isolated populations around the world including Native Americans. However most of them advanced at least to the Neolithic level. Even the Inca were in sort of an early bronze age when Europeans first arrived. Even those that didn't have metal tools, still had some sort of metallurgy in the form of jewelry.

However the Aboriginals had yet to discover agriculture or metallurgy in any sense of the word and lived in bush shelters that were no more substantial than something that can be constructed by someone who was lost in the woods. They also never developed the simple bow and arrow. In fact, the Tasmanians apparently lacked the ability to make fire and relied on a fire guard to keep an ember lit at all times. They also didn't know how to catch fish, make tools from bone, or make clothing, using one each other's body heat for warmth in winter months.