I’m really sorry to hear that. I can relate to your experience a bit, but I believe that knowing about the breeder situation and the terrible treatment your bird went through will help you be patient and keep trying.
Knowing about your bird’s trauma should motivate you to keep working on gaining their trust and restoring their faith in humanity.
I have a similar situation that I shared here. Mine is worse because he hates toys and is afraid of them, which makes him just sit in the cage doing nothing.

I also understand what you mean about cleaning the cage, the area around it, and even taking them to the vet. But we have to be consistent and not lose faith in the fact that a major breakthrough will come.
They love us. My grey loves me, and I’m pretty sure that yours loves you too, but they don’t trust our species. They are still young, and one day, they will learn that we are on their side.
Be patient. Help them have a better home. Don’t rush it. Focus on small victories—one day, they will step up, and that will be the end of this chapter in their life.