I doubt this is true. I almost always have send out personalised messages if possible (E.g. comment on something in their profile, something noteworthy in their fotos or something else). They just almost never respond(I would say <<5% even respond), and if they respond it's not much beyond an: "haha thank you" or something empty like that, with no follow up of any kind. It was impossible to keep any kind of conversation going no matter what I tried.

Now? I just gave up. I have better things to do then spend hundreds of hours without a single conversation going anywhere. Online dating is a useless black hole.