Manchester United will need Ronaldo's contribution in the remaining games as well to be able to qualify from their group easier. He scored an important goal against Sheriff Tiraspol to increase his passion to show a good performance in the coming games. But he really needs his finishing skills back as soon as possible. He wasted some really nice opportunities in that game and he was able to score thanks to a penalty. This is enough for people to mock Ronaldo about his scoring mostly by penalties. He is a legend anyway but I hope he continues to score different kind of goals more often.
I don't think it's just Ronaldo, although he is undoubtedly a key player. Manchester United are having a lot of problems inside the club right now, so they are losing a lot of games or not realising a lot of opportunities. In the old days, Manchester United would have destroyed Sheriff even without Ronaldo. By the way, their next games are not the easiest, first the game against City and then the Europa League game again.