Basically Ronaldo is a good player, it's just that the mismatch with strategy and also the many players who rely on individual skills at least makes Ronaldo's performance decrease slightly due to lack of support. Yes, I have said before that Manchester United's gameplay in the first half was very boring, it can be said that Rangnick tried to find a way by letting his team play badly at the beginning. Implementing a strategy like this will be very dangerous against a better team, I really don't think Rangnick can take advantage of the good players that Manchester United has.
Ronaldo now still try to use his speed in counter attacks of Manchester United. Even he is now old, his speed is well better than many players but he has to save his energy and only uses it in situation he see open space. So I sympathize with him in such situations when in the end he does not receive key passes from his mates.
If Manchester United can have more players with great vision and accurate passes like Bruno, they can use Ronaldo better. Sancho, Rashford, Greenwood does not have good vision.
I watched this match till the first half. Manchester United had a very annoying performance. Brighton had some good attacks in the first half. Manchester United would not have been able to win without an experienced talented goalkeeper like De Gea. De Gea saved a lot in this match. But I am happy because after a long time we have seen goals from Ronaldo. He played well. If he returns to form, maybe Manchester United will do better in the upcoming matches.
Ragnick admitted it the press conference after the match. Manchester United tried and eventually won to get 3 points but their issues are still there. If they hadn't have De Gea with amazing saves, they would have not won it. They were under pressure and faced with risk to lose 2 points. In addition, they missed some great opportunities to score a second goal, from Sancho, Ronaldo to Bruno before the very late final goal of Bruno. In previous matches, they had bad rate to change from great opportunities to goals and in the end, they ended with less than 3 points. They did not fix it in the last match.