The complaints were not that she was a woman, or that she was a foreigner or non-white. That is fundamentally offensive to the people who opposed the project.
The complaints were that a multi-million pound opera house was elitist; that the design was insufficiently flexible and didn't provide other facilities; and that the design was insufficiently 'Welsh' (the fact that basically the same design ended up in China shows that it was very 'internationalist' and not particularly context-dependent).
Now I think the design was beautiful, but that the project was a bit ill-conceived. Wales did not want an Opera House. It wanted a multi-purpose national concert and performing arts venue. It's got that with the Millennium Centre, although I'm not a massive fan of the design (to some extent it seems to be too self-consciously Welsh - slate, copper, etc).
Surely Zaha should move on after 20 years. It just gives metropolitan snobs in London (a fair few of them originally from Wales) a chance to go over old ground on the parochial Cardiff of yore, and the "disaster" of Cardiff Bay.
She's a bit of a minger as well in fairness, really hurt my eyes looking at that picture of the whinging cow earlier. She's been successful since but clearly still has a great big chip on her shoulder, she needs to get over herself.
As Jantra said above, it wasn't right for the city, at least not back then. I love the WMC because it has a little bit of Welshness about it with the slate. It may be in a false way, but being the capital city it's a little bit of another part of the country being used down there and I like that about it. Being a multi-purpose venue has also worked very well. It's firmly a part of the city for me now and we'd have a much worse place without it.