I think that's an overconfident opinion. It's entirely possible that neither Liverpool or Chelsea will have a coaching problem and have great results, what then? They'll be making excuses for the Manchester United coach again. If something isn't working it needs to change, you don't look at it hoping it will fix itself, that's not how it works. So replacing a broken element in the team would be a good idea
When it comes to the Manchester United, what is broken is the manager himself. He's not gotten that true and real connection with the team players, rather he just work with them as their manager is what I feel.