It's great that you are thinking about it. And I'm not saying that "essencse", whatever it is, doesn't exist. And sure, you could label that essence "woman" if you wanted.
But all of that has nothing whatsoever to do with the history of female people and the reason we have feminism. Sexism and all the shit that "woman" were dealt didn't happen to the people with the "woman essence", they happened, and still do happen, to the people with the female bodies. And they don't stop happening just because we decide woman is "really" some sort of inner essence.
Do you see? Woman used to mean one thing. If you want it to be this "essence" thing instead then sure, but it's a different thing. Whether it was "really" womahood all along is ultimately meaningless because if it is "womenhood", all that means is we used the wrong word for female people. It doesn't make the men with the essence somehow interchangeable with female people, or change the history or needs of female people. Whether you call us women or not, those things do not change, and whether you call men-with-the-essence women or not, they will never have those experiences and were never part of that history.
And because whether you call us women or not, we still exist, we still need words to decribe what female people experience and need and we still need the right and stage to speak.
Personally, given that Woman is the word under which the female bodied lived and were defined for hundreds of years, the word under which we knew ourselves and our history good and bad is written, I think that's the one we should keep. But even if we don't, we cannot accept the reality of female lives and experiences being recast as the story of the people with the woman-essence, because whether that is "really" womanhood or not, it is manifestly not the same thing.