One of the difficulties with this topic is generalizations about 'Native Americans'. The so-called Five Civilized Tribes of the Indian Territory had three-branch governments similar to the US with elected prinicipal and assist-principal chiefs (the Choctaw and Chickasaw used the title of 'governor'), a judicial system, and elected legislators. They had school systems and provisions for maintaining roadways (toll roads, bridges, and ferries). These 'tribes' held fee simple title to their lands -- they did not live on reservations and they were not 'wards' of the US Government. The Supreme Court coined the term 'Domestic Dependent Nations' in the 1830s.

It gets confusing considering the differences between the Plains Tribes of central and western Kansas with the Five Civilized Tribes of Indian Territory or with the numerous 'refugee' tribes (Delaware, Shawnee) and reservation tribes (Osage, New York, Sac, Fox).

Your statements about poor land for agriculture and the disappearing game applies more to tribes in Kansas and western Indian Territory and doesn't really apply to the Five Civilized Tribes.