It's been known that Bioware fucking sucks at modeling females. I remember the talks about how Miranda looked nothing like Yvonne in ME2. It's clear they need a revamp of the animations and modeling team so I don't think this was some deliberate action on the part of Bioware to depict 'plain' women so much as their team just again being fairly bad. They do much better with males as seen by Shepard and even male Ryder but for whatever reason can't exactly do the same with the female batch.