I'm afraid it's a problem of supply and demand.
Mots adopters want a child without special needs. Most waiting children have special needs.
Many adopters want only a single child, while many children are in sibling groups.
Most want a child as young as possible, so there is a lot of compettion.
Of those who express a preference on gender, most want a girl. But more than 50% of children needing familes are boys.
Most adopters are white , while many wanting children are of mixed heritage.
So there are very few children In the system that you would consider. When you find one, there is a lot of completion for that child, as you have discovered. That's why the SW for these children have not got back to you. If they have a lot of enquiries, they can afford to be very fussy about who they consider. while you feel you can only take on a low risk child, they don't have to consider higher risk families like you.
So either you will have to be prepared to wait , and hope that a SW for the type of child you want will consider you. Or you will have to be more flexible in your requirements.
This is how the system works. Everyone wants the best child for their family. Every matching SW wants the best family for their child.
Speaking to the manager or complaining will change nothing. This is how the system operates. It's about finding families for the children in care, not finding a child for parents who want one.
Sorry, I know this is very hard :-(