re: NASA pushes back dates for Artemis II and Artemis III missions.

The issues are the main engines and the technology behind them. They are still using SSMEs (Space Shuttle Main Engines) to power SLS. Once they run out of those they have to redesign or purchase them. Then they have to be certified for man rated spaceflight. The avionics and other systems are archaic at best. There are over 70,000 failure modes. Literally if printed all the failure modes off and stacked the reams of paper it would be half the height (212 ft) of the full stack. It's at least the height of the core stage. Then add to the fact the valves and other systems have to either be (a) sole sourced from a single vendor or (b) have to sit on a self and have a shelf life for the life of the vehicle....it's a poor way to run a space vehicle management.