Despite what many women think, today's high value man WILL treat a woman well–provided he actually likes and values her. And the opposite is true as well.
Men will always treat women they don't like substandard in some very obvious way. And women must learn to base a man's seriousness and level of attraction and commitment on the way she is being treated in the relationship above any other metric.
And sex doesn't count. At all. Men will have sex with just about any woman who is willing and you mustn't measure your value as a woman on a man's willingness to have sex with you. Sex means zilch in terms of how a man feels about you–it's all those other things outside of hitting the sheets that matter above all.
But I have also long discovered that men of whom you don't share the same physiognomy can and often do treat you lesser despite how objectively attractive you are. I briefly dated a pretty average guy once when I was young who had a huge thing for women who also appeared to be very average. He treated me like crap and I was chopped liver next to his preferred archetype of average woman. I couldn't figure it out until I dated a very handsome guy after and he treated me very well.