Yin Yoga is for people who need to slow down - properly slow down. If you're always rushing, always doing, always pushing through, this practice asks you to stay still and let your body soften instead.
This isn't about achievement or getting into impressive poses. You find a stretch you can feel without going to your absolute limit, then you stay in it for a few minutes.
If you're used to "pushing through" or find stillness uncomfortable, Yin will challenge you in unexpected ways. That's the point.