Good design is difficult. That's the easy to understand part.
What is difficult for me to understand, why is this skill just ignored. There are lots of skills that are difficult, but people still persist on learning them. Not for software design. It-works-somehow-for-now seems to look good enough for the most. This also results in "OOD is difficult, FP will save us. Oh no, FP does not really save us, FRP for sure will".
Sorry guys, you will need to break some eggs for omelette.