Truly this sounds alarming. Sites should 100% pay attention to these issues and act fast on any self exclusion issue. It is against their license agreements to not do that actually.
But also players that are aware of their problem shouldn't just rely on the site taking actions but also seek help themselves. Sure it's easier and convenient to just say I self exclude myself and that's it, but that's not how it works.
Gambling addiction is a serious issue and in my opinion without proper professional help this is nothing you can easily fight by yourself. I understand it's hard to share this problem with others but that's just necessary to beat this devil inside.
We cannot make a quick judgement here just because someone has posted like that. We know how SportBet.one build their reputation here and one user posted an accusation against them, though it doesn't look good but we have to be fair. @holydarkness is right, this is a service discussion thread, if he really is serious with his accusation, he needs to bring this to a proper channel of the forum which is the scam accusation board, but as @holydarkness said, there should be a valid evidence.