Also Smithfield is smothered / dominated on all sides by bog-standard apartment blocks /offices.
I don't think that's true at all and a lot of the new architecture in Belfast is not exactly tasteful or inspiring. But what matters in a public square is not so much what contains it (unless there is a major set-piece, or the whole square is an art-form like the Grand' Place/Grote Markt in Brussels),but what happens in and around it. So, you need a reason to go/be there.
Your idea of getting an outside eye to run over it is not a bad one at all; a second opinion is often reveealing, or at least inspires debate. I haven't been to Belfast recently, so can't comment on how well/badly their 'new' public places work, but Victoria Square does look very good.