The long term effects of British colonization of Australia were very similar to the long term effects of the British colonization of what is now the United States. In both cases, countries were eventually created that became wealthy and democratic. In both cases, the native peoples were devastated by the coming of the British.
British colonization of Australia led, in the long term, to the creation of the country of Australia. This is a country that is among the top tier of countries in the world in terms of wealth. It has a healthy democracy and is something of a melting pot, particularly for various groups of Europeans. (It has, at times, been much less welcoming to non-white people.) In this way, British colonization had very good effects for the people who live in Australia today and are not Aborigines.
By contrast, British colonization devastated the Aboriginal people of Australia. These people had very little technology when the British came. They had no resistance to European diseases. Those diseases, along with violence by the Europeans, decimated their population, killing as many as 90% of the Aboriginal people. The British had no respect for the Aborigines' rights or even their lives. Even after the settlers had taken all of the productive land away from the natives, they continued to treat them poorly. Abuses of Aborigines continued well into the 20th century.
In these ways, the British colonization of Australia had long term impacts that were very good for Europeans who came to live in Australia but very bad for the original inhabitants of the continent.