I used to think Manchester United signed wrong players in the past, and that is why Manchester United couldn't improve their performance, but after Manchester United sold some of the players who they thought weren't good enough to play for Manchester United to other clubs, those players performed well at their new club, and a player like Scott McTominay helped Napoli to win the Scudetto. That is when I knew Manchester United's poor performance was an internal problem, and Manchester United players aren't 100% responsible for Manchester United's poor performance. If Manchester United wants a total change at Manchester United, they should improve the things Cristiano Ronaldo pointed out were the problem why Manchester United is finding it difficult to challenge for the Premier League title.
I was hoping that you mention the things Ronaldo pointed out that can improve the team, well perhaps I missed that part in previous conversation.
One thing you should know is that, the process of rebuilding a team takes more than just selling out players and bringing new ones. It takes time to actually do it. But Manchester United is not a club that can give a coach all the time, they want instant actions. For instance you see the Mikel Arteta project, has been going on over two seasons before the team was able to be rebuild. Meaning as a coach you have 85% responsibility on the performance of the club after your debut season.