And another point, if it's not OP fault, if it's company fault I think they MUST do it as they "lost" or "block" their customer money because an error.
It's definitely Gamdom's fault and not the OPs. Gamdom is a crypto casino that doesn't charge its players any transaction fees. Also, the player can't select between different priority levels when initiating their withdrawals. If that were the case, we could say the blame is to be shared between Gamdom and the player. But it's not.
Gamdom pays for the network fees from their pockets. It seems they are sending their withdrawals (at least they did with this one) paying low fees not to waste too much of their own money. The result of that is a transaction that has been stuck for +3 weeks. Some other casinos overpay to get a quick confirmation and prevent exactly what happened to OP.