Dunno, don't care. To me male sex demon is incubus and female sex demon is succ.
I don't see the need to go out of your way to reinvent the wheel.

Except for the fact that it's not reinventing the wheel, you just don't like the current meaning of the word (yes, the meaning of words do change over time, for better or for worse).
Historically, when and where the words were used the most, "incubus" referred to a
male demon that would sexually target
female targets, while "succubus" referred to a
female demon that sexually targeted
male targets (both most often appeared in dreams and attempted to seduce the target, usually through sex). That is the general historical context, though variances (as always with myth and folklore) exist.
Now for the modern day, often the demon in question has shape-shifting capabilities, and the name is generally based on who they prey on, rather than the form the demon takes (like others have explained with the top/bottom examples), so if the
target is male, then it's a "succubus", if the
target is female, then it's an "incubus".
Depending on which work you look at, there are also a whole litany of differences on classification and how it all works, but this is the general way it is currently.