I don't know how AF will answer that question... but i can say in my own case and in the cases of many people, that yes you still love them.
I was thinking, for example, of when people in our family become addicted to drugs or alcohol. It may be impossible for us to live with them anymore, because being with them will damage us. But if it's our mother or our child or our brother... they may have changed but yes, we still love them. I have a good friend, for instance, who's brother is a heroine addict. That's tough. He's abusive. She still loves him. But no one should live with him... he'll steal or do anything to get money for a fix. So she has to let go of trying to be with him, even let go of trying to help him (as he does not want help), but that doesn't mean she has to let go of her love for him. That is not a requirement of letting go.
I can also think of my ex-husband, who had a psychotic break and changed radically in personality. He became unsafe for me to be near... both mentally and also there was concern he'd cause me bodily harm. But i don't think, "i only loved the person i thought he was," ...for he was that person i knew once. But yes, i did not know everything about him. Not even HE knew everything about him. That is not uncommon. Doesn't everybody make discoveries about themself that they never knew before? If we don't know ourselves 100%... how can we know another that way?
I think sometimes it may help to realize we didn't know all about a person, but i think saying we didn't know them and only loved an illusion, often only leads us to distrusting our own judgment.
I had known my ex 23 years, and i never would have guessed he would have been capable of some of the things he did. Once in a while i come across a person who doesn't really know me, but who judges me and thinks i can't see danger and should have seen it in him before i married him. But i'm lucky... i know conclusively that no one could have predicted my ex's mental illness... he worked among psychologists for over a decade, in a field where he was screened to qualify, and if none of the psychologists or psychiatrists he worked with suspected a serious mental illness lurking underneath, why should i have?
I guess what i'm trying to say is, sometimes a relationship goes sour and yes we still love them, and sometimes turning off the faucet of love is not an option. I have found what helps me to move on, is realizing what i stated previously... that just because you love someone, doesn't mean it is healthy to be with them. And that has let me still love them... sometimes with no contact with them... and yet STILL be able to close the book with finality and move on. Loving someone, and wanting to be with someone as they currently are is not the same thing. You can love someone, but love yourself and care for your own welfare and happiness and be committed to that. I can recognize that it is not healthy for me to have any association with my ex, and choose my own safety. I can also still love him and wish him well in life.... I DO! And somehow, being at peace with that, i am able to dream of a happy future without his presence, and look for someone with whom i CAN have a healthy, happy relationship.