There are several factors that could explain this. First of all, the Neanderthal population were of a different body type than we are. They may not have appealed to our ancestors, and vice versa.
Science Fiction used to have a lot stories in the 50's of rapes of women by lizard men, etc. Why would this occur? Would a lizard man find a homo sapien woman any more appealing than you would find a lizard woman? Something to think about.
Also, the Neanderthal population may not have been as thick on the ground as our ancestors were. Their language, brainpower and hunting skills may not have been as developed as our ancestors. The gestation rate for Neanderthals was also different from that of our ancestors.
All of these factors combined might have something to do with their demise.
Finally, genetic differences could play into this. Even if you're attracted to a horse, no offspring will be produced. You don't see hybrid horse and zebra offspring out and about, do you? The DNA match isn't there. The article you refer assumes that reproduction is possible. It may not have been no matter how many times copulation occured, simply because the DNA sequences were off just enough to say "no."
Yes! There are horse and zebra off spring alive today, I've seen pictures of them. Regardless, I got your point when you used that as an analogy.
A Zorse is a Zorse of course of course and no on can talk to a Zorse of course that is of course unless the Zorse is the famous Mr. Ed.