I have been dealing with this for over 2 years, that is a great observation.
A little history, the male is 26 and my parents had since he was a baby and was actually hand raised. He was abused by my father (he would beat him when he got out of line), and he was barely ever let out of the cage. Fast forward and he is nasty, lunges at me, and I can not physically interact with him. He does talk and will sit there and have a whole conversation with me. My Mom has passed, and my Father is dying...it makes the decision hard since he is part of my history and has their voices. I also think he has more potential if he could stop being so angry.
My other amazon is a 24 year old female. Very sweet, but just screams and screams, does not talk. Has not been handled much so she doesn't even know how to perch on arm. However, you can pet her and she likes it...a bit too much though. She is prone to getting excited and laying eggs. She was not abused as bad as the male, and she has an overall better temperament. However, she has learned/picked up nothing in years, I have a feeling it is because she is female, she isn't a talker at all. I don't believe she has much potential, but as a companion who you can pet all day and if you can minimize the screaming, she is perfect.
These two are not mated per say, but they have been in the same room for 20 years, and haven't been separated. Not sure if that would help or hurt. My husband and step son refuse to bother with them besides cleaning, so I am the only one that will and I seriously don't get much time between having other birds, and two dogs. However, it seems like they need a LOT of time to get to where they need to be, and I do have other birds I need to spread the time out to (two cockatiels, a senegal, and parakeets - although the parakeets don't really like interaction as much as the others).