The Who is Donna Troy isn't a retcon, it's an expansion of the bare bones story they gave her in TT.
Crisis screwed her origin up... Moreso the PTB at DC did that. Rumor is that George wanted the start of his reboot of WW to be a sort of Year One, and then the rest of the run being "now". And that would have allowed him to work in the WG stuff. But DC likes the idea of Diana arriving later in the age of heroes (after Kal and Bruce, etc) so that screwed everything up, and needed to be addressed by Marv and George with the Who is Wonder Girl? Retcon ( the first retcon)
That all would have been fine. They could have even tweaked things once they returned Diana's debut to earlier, melding the Amazons and Titans of Myth parts of her history.
But then she died and came back and was retconned by Byrne, by Infinite.Crisis, by the 52, etc etc etc. Changes to fix changes to fix mistakes from.changes.
None of that other stuff was her or Marv's fault, but of screwy editors not respecting what came before and wanting to put their stamp on it.