First, I feel that the language you used is, how to say it, presumptuous in the least. Were China and Japan not "ambitious" enough to make overseas colonies? That's not the question you should be asking. Rather, the question should be "Is there any reason at all why these countries should be interested in colonizing Australia?", which then leads to the question "Is there actually anything of real value to a colonial empire in Australia?"

Answering the latter, no, like really no. Australia was colonized in 1788, 182 years after it was first discovered and basically the end of the Age of Discovery, not because it had any real resources to exploit but because the British wanted someplace else to send their prisoners after the American Revolution and because the British wanted a foothold to counter French expansion in the Pacific. I cannot stress enough how little the continent of Australia had to offer in trade or resources to any would be conquerors, especially when they could go to literally anywhere else in Southeast Asia or Southern China before reaching it.

Speaking of China, it has, historically, had very little incentive to expand eastward into the Pacific, none the least because their northern and eastern borders were both more lucrative and dangerous. That is no to say that imperial China had no interest in the maritime Southeast, but they had no real interest in ruling those lands when they could just exact tribute instead. If we take the time period you mentioned, the Age of Discovery, then we get a time period spanning the Ming and into the Qing Dynasties. For the Ming, control of their already substantial land empire was their first and foremost priority, dealing with remnants of the previous Mongol Yuan, putting down internal rebellions and fighting off pirates off their coasts. That is not to say the Ming Dynasty didn't explore, after its under its flag that Zheng He led his seven treasure voyages as far west as Arabia. Not however, that doesn't include Australia, because, again, why would you go to Australia when you can go literally anywhere else. Granted, the Ming let their navy rot afterwards but China has always been a land based empire, akin to the United States, and only in the modern era have they shown any real interest in becoming a maritime empire. Much of the same can be said for the Qing with the addition that by that time the European powers had already colonized much of Southeast Asia anyways.

As for Japan, that's even easier. Japan at the time was in the Muromachi period, the first 50 years of which were embroiled in the Nanboku-chō period, a civil war that lasted from 1336 to 1392. In 1467, Japan entered yet another civil war, the Ōnin War which started the Sengoku Period, a time of near constant civil war that lasted until 1615. In the midst of this, in 1592, after an initial unification under Toyotomi Hideyoshi, Japan then attempted to invade China by through Korea in the Imjin Wars which ended with Hideyoshi's death and caused another round of political turmoil. After Tokugawa Ieyasu took control and established the Tokugawa Shogunate, his grandson Tokugawa Iemitsh enacted the sakoku policy of complete isolationism that lasted until 1853. Part of the reason of this policy was to combat European expansion, specifically against the Spanish and the Portugese. There are other reasons as well, but the fear of being conquered and made into another colonial possession was a driving force behind it.

Thus the answer to your question. First, there is very little reason anybody would want to colonize Australia except for wanting more land and, in the case of the British, wanting a place to put prisoners after the American Revolution. Second, China has historically cared more about expanding westward and were already busy enough securing their land borders and dealing with internal conflicts to care about the Pacific. Thirdly, Japan was in no position to expand due to careening from civil war to civil war and by the time the country was unified it was already surrounded European colonies.

More can of course be said, but there's an FAQ section on Australian contacts with Asia which can be found here, containing in particular two answers, one by /u/PangeranDipanagara and one by /u/mikedash.

So, it feels a bit like there's an assumption that large, organized countries would default to colonizing. There's no such thing. Trade networks are another thing entirely.

Note: I used inconsistent terms for the Dutch East Asia Company (VOC). Any mention of the Dutch is in reference to the VOC.

It's well documented that Makassar merchants from Sulawesi were trading in northern Australia at least 300 years ago. Makassar merchants were in an ideal location between SE Asia and Oceania-Australia, along with India and Europe for international trade. Well within the trade routes of China, it is conceivable to believe that Chinese traders and imperial officials involved in international exchange would have been aware of the Australian continent, if only in reference to the northernmost point. Some of the best evidence available of Makassar activity in Australia is the trepang exchange, a type of sea cucumber collected by the local Yolngu in Arnhem Land, Australia.

The trapang has been a trade item for at least a thousand years between various groups in Eastern and SE Asia. For the Makassar, even during European occupancy, their trepang clients were either Chinese merchants or what is now Singapore (Máñez & Ferse, 2010). They were in the right place at the right time when the product's popularity reached new highs in the 17th-19th centuries.

China was the principle harvester and importer of trepang in general since at least 1602, with "written references to trepang appeared for the first time under its Mandarin name haishen (sea ginseng) in a book called Miscellanies of Five Items"(Máñez & Ferse, 2010: 2). Due to its new popularity and its reputation as an aphrodisiac and medicine, over time supplies of trepang from coastal China were incapable of supporting demand. Japan, SE Asia, the Indonesian archipelago, and eventually Arnhem Land and beyond were exchanging dried sea cucumbers to merchants that ultimately delivered the product to China. It's recorded by the Makassar Harbormaster in 1814 that of the products exchanged with the Chinese merchants: " the so-called trepang Marégéq [Australian trepang] is the most prominent, and in China the most sought after, and sold there for a very high price"(Sutherland, 2000: 76).

The year 1814 is a bit late but there are earlier recordings and room for interpretation. The occupying Dutch Company's official record of allowing exchange with China in Makassar is 1731, with the first recorded transaction in 1736. Yet in 1732, ten Chinese Nakhoda -representatives from Chinese trade junks - complained about the difficulty of buying trepang in Makassar due to weight-connected taxes imposed on the trepangers (Sutherland, 2000: 83). These taxes were waived for that time, although it is unclear to me for how long this exemption lasted. If complaints were made about a change to the status quo, this indicates that a previously more favorable arrangement must have existed.

The ethnic group, Wajo, in Makassar have an even older history of intracoastal trade and migration, and with them came the code of Amanna Gappa written around 1670 used extensively for foreign trade (Sulistyo, 2020). As a code of ethics that was applied to international trade, combined with the mentioned record of a tax exemption decades later: those Chinese traders in 1732 were frustrated at the change of the trading process, so I believe their relationship with Makassar must have existed before the Dutch monopoly.

There is evidence of further contact with Arnhem Land from the middle of the 16th century. Yellow beeswax based paints from rock art in Djulirri depict Indonesian and Malaysian praus, a type of ship design that the Makassar people used. With a reported range from 1517- 1664 and a median age of 1577, this rock art " is earlier than even the most liberal estimates of when Macassans are thought to have first begun trepanging in northern Australia" (Taçon et al, 2010: 6).

It needs to be expressed that older material evidence of outside interaction with the Australian continent does exist - eg the Makassar predecessors, probably the Baju, Wajo, - with plenty of contrasting debate from researchers. Pottery sherds, foreign imports (like non-endemic shells, tobacco, and woods), and atypical settlements and material processing camps that are alien to northern Australia but appear identical to other cultures from the Indonesian archipelago all serve as examples of outside contact that appear to be contained in briefly lived contact zones of cultural exchange. Indeed, it's from the 18th century trepang exchange that the vast majority of substantial Makassar material and linguistic influence in the Yolngu Matha language group can be found (Bilous, 2011: 378). Whether the Yolngu were conscious of it or not, they were connected to Eastern Asia well before European colonization.

Bilous, Rebecca H. (2015). Making connections: Hearing and sharing Macassan‐Yolηu stories. Asia Pacific Viewpoint, 56(3), 365–379.

Máñez, Kathleen Schwerdtner, & Ferse, Sebastian C A. (2010). The history of Makassan trepang fishing and trade. PloS One, 5(6), e11346, 1-8.

Sulistyo, Bambang. (2020). Trade and ETHNICITY: Business ethics and the glory of maritime trade of THE MAKASSAR’S Wajorese in the 18th century. Journal of Maritime Studies and National Integration, 4(2), 108-114. doi:10.14710/jmsni.v4i2.9610

Sutherland, Heather. (2000). Trepang and wangkang: The China trade of eighteenth-century Makassar c. 1720s-1840s. Bijdragen Tot De Taal-, Land- En Volkenkunde, 156(3), 451-472.

I highly recommend Sutherland's article if you're interested in the highly organized trepang trade.

Taçon, Paul S.C, May, Sally K, Stewart J. Fallon, Meg Travers, Daryl Wesley & Ronald Lamilami. (2010). A Minimum Age For Early Depictions Of Southeast Asian Praus in the Rock Art of Arnhem Land, Northern Territory, Australian Archaeology, 71:1, 1-10.