Vocal-wise... maybe, but I never had any problems with Riho's to begin with so that's fine by me.
Stage performance ability? Riho is the same age as Goto joined now and imo she's way ahead of her. Even by Ai no Bakayarou she still looked all kinds of awkward to me.
My point is, it's still too early to hand out judgements like it's the most obvious fact in the world

. Give her some time, maybe she'll catch up to Maki vocal-wise like how Maki herself eventually become more interesting to watch on stage in her later career.