This is not fair at all. Yes, I have seen casinos require their players to wager 50x or more if they take deposit, welcome, or other kinds of bonuses. That make sense because they won't give you something for free. You have to play there and you have to win. I also saw casinos need a wager requirement for any deposits to prevent money laundering. But, it was no more than 1x. Having five times wagering requirements on each deposit is not fair at all.
You should avoid that kind of casino at any cost. Of course, you have to read their ToS before you sign up and make a deposit. Because they may already mention this term on their ToS page. If you can make your first withdrawal from their platform, run away with your money and never look back. Those casinos are designed to steal money from users.
It's not fair, but that's how it's always been. Some gamblers manage to win some money but have to pass the wagering requirements before withdrawing the money, especially when they follow a promo given by the casino. If the wagering requirement is under 10x, it will be fine as it is not too demanding. But usually, casinos enforce high wagering requirements, so only a few gamblers manage to pass those requirements and withdraw their money. Before joining any promo, we must make sure we know the requirements so that we are not disappointed and only take part in promotions that we can afford so that we don't use a lot of money to participate.
When they give you some money, it's not for free. They are on the market to do business with you. Sometimes in an unfair way. Since players accept the rules/terms of the bonus, they must fulfill the wagering requirement. Yes, that's how it's always been. But when we talk about the regular deposit wager requirement, it's unfair for any casino to force their players to ask to wager more than 1x to be eligible for withdrawal.