The main aim of signing Ronaldo for Juventus was clearly to win the Champions league, which they didn’t achieve. I see this as the main reason why people claim Ronaldo wasn’t a good signing for Juventus. As well as him being one of the main reasons for Juventus’ economic issues.
The guy was a the literal definition of carrying a team on his shoulders for Juventus. Unfortunately the team had deadwood in midfield and an aging defence but still he managed to drag them up the UCL for a while, especially his trademark singlehandedly destroying Atletico Madrid.