If Ronaldo can be trusted by the coach and has a good impact on the Red Devils' game, I think playing Ronaldo from the first minute is a good choice. this must be done to secure a quick goal to be made.
but I don't think United's problem is that. they are not a club lacking good players. but they couldn't show an effective game. they hold the ball very long but don't plan the attack well.
but I am not sure, Ronaldo's game can be a differentiator in United's game later.
That is your perception and I think if Ronaldo was played in the first half maybe Manchester United could have played more aggressively in the first half. The first half was so chaotic in defense and midfield that they looked easily overpowered by deadly passes from opposing players. but it's an early game and there are still 37 rounds to go I think erik can make the best of it to get 3 points. there were no major changes that took place in the manchester united squad in this summer window which made their playing situation unchanged like last season.