I'll be honest, spinning kicks are never going to be my forte (more of a spinning backfist guy).
As a beginner, the advanced head spin kicks aren't part of the required for my grade, but I struggled alone with this and after a year analyzing on heavy bag and in kumite, and also asking the instructors, I first thought I just didn't get the technique right, I realize now that the culprit for me is my low flexibility and mobility, rather that that i don't understand the technique. I ended up using my back instead to compensate for the lack of flexibility, which isn't good, i still got some hip and lowwer back pain. But I have realized this now, finally! It was a releif. After all, I am not 20
Spinning kicks to liver or opponents thights are easier and they can be pretty powerful. I found accidentely two times during sparring there is a "magic spot" that if you hit somewhere below the hip and upper thigh with a ushiro mawashi geri, that almost paralyses the opponents leg for some minutes. But its more potluck than skill to hit it I think, at least for me.
I realized this even more than asking my physioterapist and she measured my hip external and internal rotation. For my physiology I simply have a hard time to do certain kicks, but a bonus is that there are other kicks (which hard harder for normal people) that is easier for me as my flexibility was like a baby according to physioterapuet, like angled 45 degree axe kicks from the outside, which are pretty nastf it hitting the sides, only issue is that they are easy to get leg catched! So one has to hit hard enough to take the breath out of them.
So right now i tried to develop my fighting skillset to utilized not what others do, but what works best for me own limits.