Perhaps the feelings were not mutual. There's nothing wrong with that. I still don't think you have been 'officially' doorslammed. At least from what you say, I can't really tell. But when you are really doorslammed, you will know and understand that it was you that failed because the infj will tell you again and again and again and again that "blah blah blah" is not acceptable. You will have an opportunity to improve the situation. You will even be directed on how to remedy the situation. An infj will articulate the problem in easy to understand terms and allow it to be fixed, before a doorslam occurs. It's not an imbalanced relationship. It's not a mystery. If anything the infj puts up with more shit that your average person.
Yes, this is true. They are accepting of many different flavors. However, romantic relationships are not the same as friendship, acquaintances, strangers.
It seems that you are having a tough time understanding what a 'doorslam' is. A healthy infj will inform you many times of a situation that needs a remedy. You will have more than a healthy amount of opportunities to address the situation in any way you seem fit. If you refuse or if you are not capable of trying or able to do anything, goodbye. The doorslam is a long process, but it is not a mystery.
Perhaps you have been ghosted of simply broken up with? What is the situation with which you struggle?