I have only used one and while I’m sure the site is legitimate (it’s a huge one that’s been around a while and has tens of millions of users), every person I met on it was a total creep or scammer. Over about a year I chatted with probably 200 people and not one of them was legit! No more of those sites for me, total waste of time and a real wake up to how many fakes and scammers there are in the world today. Sad.
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.

Thank you for your comment, I appreciate.