One of the problems with cryogenic fuel (liquid oxygen and liquid hydrogen - Artemis; or Methane for SpaceX) is its hard to pre-cool the valves to -450 C and then fire the rocket without thermal issues. Expansions s contraction at the extreme temperatures are hell on seals. Jamming (or freezing in place) is all too common
Apollo used Kerosene and liquid Oxygen- better risk tree; imho
Not only "hard" - completely impossible (-450 °C is below Absolute Zero).
Regards,