[2021] What do I do as Leona in late long game?

When a game goes past ~35 mins if my team isn't well ahead and playing as a team well idk what to do. If I engage the enemy team ( w,e,q,r) I just get melted and my team often won't pick up a single kill. My normal play is to babysit the adc or whoever is carrying in later game and engage for them but if that's not working I have no backup plan.