People who are leaning towards Ronaldo:
1. Short sighted
2. Don't rate Mbappe as one of the best potential youngsters.
3. Overvaluing Ronaldo's future value.
or all three.
For you, 1 and 3 indeed.
I agree goals are invaluable aspect, but sacrificing other aspects just for goals isn't good enough. People argued against Chicharito because of the same reason that he wasn't doing enough on our build ups to be our starting forward. Also with Ronaldo's constant moaning reactions toward his teammates would definitely undermine team spirit. You highlighted Ronaldo's goal scoring value, but I seem it is just little overvalued considering other aspects.
And yes Ronaldo would be a better choice at the moment. But thats just "at the moment". We have to think long term and plan about how to win CL, not just the league. That is our ultimate goal, winning the league and CL as Man Utd. Yes Ronaldo may help us to win PL this or next year, but do we currently have strong enough squad to win CL? It's debatable, but I would say not currently. I would rather work on improving the squad in order to win CL in 2-3 year time, and I genuinely believe with improvements of our youngsters and few transfers, we have a good chance. That would be a bad time to worry about offloading declined Ronaldo.