I have never been on a dating site but people I have known who have used them got a wide range of results or uses.
One friend found someone to marry while another just used it as a site for hookups. Of course the later was not the I tended use for the particular site. But it has evolved into that unfortunately.
It is the people who make the sites genuine. So whoever operates the site must be very restrictive in order to keep it genuine I think.