First of all, the scope of archaeological excavation is not limited to tombs. Ancient human settlements, city sites, workshops and other ancient relics related to human activities are all archaeological objects. The problem of "cremation" is limited to tombs. Thousands of years later, when we become ancients, the scope of archaeology will not be limited to this.
Secondly, the purpose of archaeology is to study the life of ancient human beings through physical remains, which will inspire today's society. China experienced more than one million years from the Paleolithic Age to the late Qing Dynasty and the Republic of China. Even after such a long change, historians, political scientists, writers and other researchers in various fields can study ancient politics, economy, thought, culture and daily life, from economic foundation to superstructure, with the help of archaeological excavations. Tomb archaeology is very important, because ancient tombs can let us know about the ancient tomb system, clan relationship and hierarchy. The ancient tomb further reflects the real life. However, the big framework of today's social structure can not be reflected by a grave. Today's society is no longer the master, breaking the relationship between the feudal system and the clan, so today's tomb archaeology is of little significance.
Finally, archaeology has a wide range and rich content, but it is basically concentrated on human beings themselves. Ancient information records were not developed. Although ancient books are voluminous, they are still not enough for people today to do research without dead ends. Nowadays, the amount of information storage is huge, and all kinds of information about human beings, such as medicine, science and literature, can be found through the internet. To put it simply and rudely, as long as there is the internet after thousands of years, there is no fear of not understanding the current social situation. As for cremation, it will not have much impact on archaeology in the future.