For me I have totally lost interest in them, there’s no way I’m going back to the site [I don’t have any balance there] - if I’m allowed to delete my account I’d gladly do so without being able to log in ever again.
Theoretically, it could be done through a support request. However, as you've probably already noticed, getting feedback from them is no easy task. Even if their site had an option to delete your account, what would be the point? I mean that if you have lost interest in the site, forget and don't use it, especially if you don't have any funds there.