As of August 2023, Twitter does not have a block limit. You can block as many accounts as you want. However, there are some restrictions on how quickly you can block accounts. For example, you can only block up to 400 accounts per day. If you try to block more than that, you will receive an error message.
It’s important to note that Elon Musk, the owner of Twitter, has said that he wants to remove the block function and that he believes the block function “makes no sense.” However, it is unclear when or if he will make changes to the block function.