These new conditions may seem harsh, but in the end it is their exchange and they are free to set the conditions they want and the user is free to accept or not, but when you agree to the terms of service, you become obligated to implement all the laws of the exchange and you have no right to complain, from the point of view of the exchange if you do not want to trade so why keep your money there? If you keep it there you have to pay a fee for it.
Therefore, the best solution for those who do not wish to trade in this bear market is to withdraw those assets into a safe wallet instead of leaving them idle there without trading. I don't blame them frankly because the exchanges exist for trading and not for storing money. If the exchanges don't take trading fees how can they keep going?.
It's sad to still read in 2022 this kind of words. No, crypto users are not ships or cows ready to be milked by platforms. And exchanges are not free to do what they want with their customers, because scamming people is forbidden anywhere on earth.
As you said when an user registers into a platform he agrees the ToS, then if the platform doesn't want to respect them anymore and wants to change them they must offer a compensation for not respecting the initial contract anymore. Did Bitstamp at least offer to users to withdraw their funds without any withdrawal fees and KYC? I didn't hear that.
They've just tried to apply this new condition because they have the strictest KYC rules of all the exchanges afaik and many accounts are not accessible by their owners anymore because of that. But fortunately they've failed.