It doesn`t matter what they do, decrease bet limit, ban account or setting withdrawal limit. They can do it using the ToS and you can only try to choose casino without such paragraphs, but it mostly mean, that you don`t find it. And when they need - they show it to you.
I think that it is possible to find casino without such paragraphs, but it is really hard and casino willn`t be well-known.
Actually, it does matter what they do. A gambler should indeed read the terms and conditions of a casino before joining so that everything is clear from the beginning, however, if a casino changes things later on and doesn't even inform the gamblers about it, I would consider that a red flag.
There wouldn't be a problem if they had the rule from the beginning, and if they were to make changes, they should have announced it and informed all the players by showing a popup when they sign up, informing them about the changes just like how Stake and other reputable platforms do it.
I would blame the gambler if they hadn't read the rules and then faced some problem, but if the rules have been changed, the gambler isn't wrong.