Treating girls like they're holy beings that need to be worshipped seems to be the biggest problem among most dudes, but especially your typical 'nice' guy. Essentially it's pedestalising girls because they're girls. Because they have vaginas and boobs, and they have nice shiny hair, they smell nice and they never shit or fart.
As nice and gentlemen-like you think you're being, you're actually not doing yourself or her any favours. You're making yourself look kinda needy and showing her that you don't understand women very well.
Holding doors open for her, buying her dinner, pulling her seat out before she can sit, agreeing with everything she says, driving miles to be her taxi driver etc doesn't make you more desirable like you may think. It makes you look beneath her. Girls are well aware they're just human and flawed, so when a guy acts like he's lower than her (which is what you're doing when you pedestalise a girl) she will think just that. She will think you're beneath her.
If you ever have the experience of a super needy girl who'll do anything for you, you won't need me to tell you this, you'll already understand how off-putting it can be.
Once you get to know a fair few attractive girls, you'll soon realise that they're just as human and normal as anyone else. You'll be able to appreciate their appearance, but you'll be able to look past it and see the very normal and flawed human underneath. Just as human and flawed like the rest of us.
That's why I quite dislike it when I'm with another guy, and they see a hot girl and make the usual comments like "omg man, look at that ass" or "she's a babe!" It happens fairly often at work seeing as I work on bondi beach where everyone is constantly half-naked. I just find myself thinking: is that really the only thing you can think of when you look at that girl?
As my ex-girlfriend (but still best friend) says, "when a guy acts all gentleman-like and treats me like I'm royalty, it can be nice but it just makes me feel like I'm completely out of his league. Like I could be friends with him, but I'd never want to sleep with him or anything." And that, pretty much summed up, is the friend zone.
Another point is, to sleep with a hot girl you don't have to do anything different compared to an average one. However, the more attractive the girl the harder it is to look past her face, massive boobs in your face, and her jeans being pushed to the limit by her fat ass. The best advice for hotter girls is to, in fact, do nothing differently at all. Don't treat them any different and don't pedestalise them. If you do alright with 6s and 7s, but fail with 8+, I guarantee that's what you're doing. It's the simplest piece of advice but also the hardest thing to do.
To finish off, I'm not saying to treat girls badly, or be rude or mean, or to never do nice things for her. But simply compare what you do for a girl, with what you would do for one of your guy friends. Would you buy your guy friends fancy dinners? Would you agree with every single thing your guy friends said, even if you strongly disagree with them? Would you bombard your guy friends with compliments? Probably not. You should be a nice guy but you should also be authentic and have some self respect. You should have boundaries and treat then like normal human beings. It's the typical "Nice guys finish last," thing. No, nice guys don't finish last, push overs do.
So be kind, be funny, be spontaneous, caring, interesting and exciting but still, treat her like she's your equal, not like a princess.