They had it coming and should quietly accept their fate.
Not really. That is exactly what the scammers want, for people to just give up their lost funds and walk away. Instead, they should do whatever they need to in their local jurisdiction to report this fraudulent scam. At least that way there's a chance the criminals will eventually be held to account for their theft.
That the website is still up will serve to show it is still attempting to defraud people. Also, that the website is still running means there'll be a live electronic trail back to whomever is currently responsible for it.
So the longer it remains, even under its current mode of diminishing-payouts ponzi-script operation, the more time an investigation has to probe its operation and track down the guilty.
You seriously think that is going to work? If you show me 1 single Satoshi recovered from that site in court or through a legal manner I will double whatever you recover. That is why these sites work because there is absolutely nothing you can do and you and every person that has wasted their time trying to recover funds should know this. You are now taking time that you could be using to actually produce income and wasting it in the same manner as when you invested in the first place.