Brant Gardner notes that Zeniff specifically notes two things about the Lamanites in the land of Nephi-- that they were "lazy and idolatrous" (Mosiah 9:12).
The term "lazy" is certainly linked to the Lamanite desire for tribute, since it is given as a justification for the conquest and tribute pattern. But the reader should take care not to infer too much else about the term "lazy." The later Aztecs of Tenochtitlan (the city of Motecuhzoma) exacted tribute from many city states, but could hardly be called lazy.
The description of the Lamanites as "idolatrous" is a very specific designation dealing with religion. One becomes "idolatrous" when they turn to idols, and thus away from God. This process is inherently religious, but with the tight connection between religion and culture in the ancient world, it is also a turn to a different cultural system. Thus Zeniff is describing a religious cultural system that is opposed to the belief in the God of Israel. He is noting that the Nephites who are now termed Lamanites have changed their religion as well as their political allegiance. [Brant Gardner, "Book of Mormon Commentary," [http://www.highfiber.com/] ~nahualli/LDStopics/Mosiah/Mosiah9.htm, p. 16]