Can GNI per capita be used to measure human development instead of the HDI?

No. Income is a means to human development, not its end. GNI per capita only reflects average national income. It does not reveal how that income is spent, nor whether it translates to better health, education, and other human development outcomes. In fact, comparing the GNI per capita rankings and the HDI rankings of countries can reveal much about the results of national policy choices. Equatorial Guinea with the GNI per capita of $13,944 (PPP$) has a GNI rank of 88, but an HDI rank 145 – almost the same HDI as Zambia whose GNI per capita is only $3,326 (PPP$).