Things like providing baby hair variations, more skin variations, clothing options and crib variations should be easy enough for them to do.
I don't know what the developers problem is with babies. Sims can carry objects and pets and toddlers and put them in specific places, so why not babies?
I don't understand what the difficulty is to enable them to be placed in other baby-specific items. A baby bath, a swing, on a play mat, in a bouncer chair, in a pram. And why can't they give them a blanket for their crib?
The whole baby scenario has always felt like a case of just about acceptable so it'll do. Nobody has complained too much about it, so they got away with that one.