The government has a responsibility to its people, not to "humanity" and to that end it has a responsibility to help them provide the basics of food and shelter.
On the food end of this, the presence of huge tracts of wasted land (for empty and unused land is wasted land), the extremely low levels of productivity of the farmers as measured by yields, and the continued problems with food security call for something to be done. The usual phobia against foreign land grabs needs to be reconsidered.
Are there not schemes that can be set up where a central commercial farm provides benefits to smaller farms, be that on an out-grower scheme, sharing of infrastructure (e.g. irrigation), provision of inputs, etc? As far as I know Tanzania has such a scheme in mind.
The problems in Tanzania, and anywhere, come down to capital. Capital in Tanzania is in short supply, and therefore it needs to be imported. Imported capital needs to be offered a return, for the good of both the foreign entity and the country. Continued status as hand-out receives is detrimental to those receiving it. Tanzania, and other similar countries, need to move to being a partner of foreign investors, setting friendly and mutually beneficial terms for co-operation. Agriculture is the obvious place to start because the continued status-quo will not raise employment levels nor will it address food security issues.