You said it yourself. You're 3.8* but 1* at LN. I don't think anyone should try making it more convoluted than that. It's like saying "I'm good at mage class but suck at warrior class, how good of a player am I?".
That said, the one of many differences between rhythm games and rpgs is that you need to get good at LN, especially for 4*. You don't need to get good at warrior in most rpgs.
So, with that said, how do you miss? I've seen many ways to miss on LN: Simply releasing early, releasing early because another LN starts but you're not supposed to unhold that LN until a bit later, notes in other lane causing you to release since your fingers want to sync with that movement, lack of comprehending LN walls, having to hold an LN in the middle of a stream, LNs short enough that you have to release them fast but long enough that you need to hold them for a bit, you get it. So which is it? How do you suck at LN?