Why Is It So Difficult to Make Jet Engines?

Currently, dadeo is in talks with safra. Safran abemanu says i recently read us offering india to jointly manufacture jet engine for our a m c e a. M c is a, then, the fifth generation jet fighter that india is currently developing. So why making and manufacturing jet engines is so difficult for india? Especially when considered that india already has crioginic engines and indigenously developed missile launche systems.