I wouldn't say he makes them worse, he just doesn't improve them.Ronaldo is a great player. However, when they signed him I said he'd make Man Utd worse and I stand by that. He is forcing them to change their style of play and the goals/contributions from other attacking players have dropped off significantly since he arrived.
I'd much rather face a Man Utd side with Ronaldo in it, than one without him in it.
Like you say, Utd have to change the way they play to accomodate him.
If you actually look at the numbers, despite all the mind boggling goalscoring stats, his conversion rate over his career is only just above average. He's just always played in teams that attack relentlessly, dominate games & create a ton of chances.
Doesn't really sound like Solskjaer's "why play a holding midfielder when you can play two" philosophy.
Still, all that said, we're still probably going to get buggered senseless which is intensely annoying. Shouldn't be happening.