The Online Safety Act asks adult sites to keep children away from pornography. On Only Dating, an age check is optional. It is there if you want to see explicit photos. Without it, those photos stay blurred.
You can join, write a profile, and message people without uploading an identity document. The check is about explicit media, not about whether you are allowed to have an account.
The full legal wording is on our Online Safety Act page. If you are unsure what a photo shows before you open it, leave the check off and it stays blurred.