As someone who successfully broke out of the “nice guy” mold, here’s what I think.
First, “nice guys” don’t relate to women as people. They’re thought of as some kind of vaguely mysterious beings who live in our world, but aren’t quite of this world. And they treat them accordingly- in the abstract, with a calculated set of behaviors engineered to try and lure them in for sex or a relationship or whatever. Not quite a mechanistic expectation, but pretty close to it.
A good example, would be a “nice guy” actually getting a first date and fucking it up. The guy would ask the girl out, get a ‘yes’, and then proceed to set up a far too elaborate first date- expensive dinner, drinks, etc… which likely would make the woman uncomfortable because she’s feeling like there are expectations involved. Then later, when she turns him down for a 2nd date, he thinks 'WTF is wrong with that chick? I just spent $150 on a date with her, and she won’t even go out a second time!" and the woman is thinking something like “That was weird… he spent $150 on me… on a first date? What’s he about?”
The trick is to make yourself seem pursuable to the woman. Someone they’d like to get to know better. A way to do this is to have a very low pressure first date. Like a cup of coffee somewhere earlier in the evening- talk for an hour or two, then end the date there. Leave her wanting more, or if you’re not interested, then you didn’t waste much of your time or money, or hers. Then, the second date can be something a little more elaborate- dinner or something like that.
It’s probably different if you’re already friends with the woman, but in that case, the real trick is not to change the way you behave; that’ll seem really weird if you go from being a friendly sort to someone who’s obviously angling to get in their panties.
Probably the single worst thing that “nice guys” do is to put way too much emotional weight on a first date. This plays into the whole doing too much thing I listed above- beyond trying to elicit some kind of stimulus response, they’re coming across as super-desperate, which is about the least sexy thing possible in most women’s minds. That’s one more reason that a low-key first date that you end is good- you come across as more confident, and maybe a little like you don’t need them, which is paradoxically (to the nice guy) an attractive thing to women.
And to reference what P-Man was saying about “Not Yes = No”… I used to think that way as well. Eventually I decided to flip it around and work it the other direction (Not No = Yes), under the assumption that I trust the woman to actually say “NO” in a coherent way. And it worked! I’d been terrified from one of the early college “NO means NO” indoctrinations that we all had to attend, and never really realized that it didn’t really mean that “Not Yes = No”, but rather literally that No = No, and that No doesn’t mean maybe.