A whole lot of women do not orgasm from vaginal intercourse unless one partner is stimulating the women’s clitoris manually or with a vibrator. In my experience about half of the female partners I have had have been able to at least with some frequency. If you look around the internet, you will find surveys of women that suggest that anywhere from 50 to 80% of women don’t orgasm from vaginal intercourse (or rarely do), depending on the survey.
But all the women I have been with who weren’t able to come from vaginal penetration only still enjoyed it. I have a difficult time reaching orgasm from getting sucked off, but I still love it.
I’ve been married a long time, but before marriage I was about 7 inches long and there were a couple of girls that had discomfort from me ramming their cervix, so 7 1/2 inches could certainly be too long for some.
And I agree, for those women who did regularly have orgasm from vaginal intercourse only, a key was maintaining firm pelvic contact with their clitoris with a lot of rocking and grinding motion.