You seem to be confused about the reasons. Fully automated flight is technically feasible (with the right equipment) under normal conditions. However, it will never be a replacement for a pair of human pilots for Part 121 commercial passenger flights — at least not without some fundamental advancement in AGI. The problem is not with routine flight operations but with emergency procedures. By their very nature, emergencies can't be anticipated and it's impossible to write code in advance to handle them. Whereas humans can improvise solutions on the fly based on first principles. A prime example is US Airways Flight 1549 "Miracle on the Hudson" where the pilots intentionally disregarded parts of the emergency checklist to safely ditch in the water.

The Garmin Autonomí autoland system is an amazing technical achievement but it's intended as a last-ditch way to save the passengers when a Part 91 single pilot is incapacitated. It would never be approved for routine non-emergency use and can't even take VHF radio instructions from controllers.