Yoru, the most recent agent, has decent playrate at 14.7%, but has an atrocious winrate of 44.9%, which is far below any other agent. Skye, on the other hand, has a slightly below average win rate of 48.3%, but has the lowest playrate of any Agent at just 8.8%. She is literally the only agent with a pick rate below 10%.

Personally, I think it will be harder for Riot will have a harder time fixing Skye than Yoru. Yoru has a decent (if below average) pick rate and a very low win rate, so they can afford to buff him and keep him relevant. Skye, on the other hand, has the lowest pick rate and her win rate is not too bad. They have very little scope for buffs without making her OP.

Source: https://www.valorbuff.com/agents