What are you talking about? How is Messi in decline? 54 goals/16 asists in 52 matches in 16/17 season. How is that a decline? Ronaldo is not getting more effective, but he does play in a better team.
Football is still a team sport, so that counts a lot.
By suggesting he's in slight decline doesn't mean he's suddenly gone rubbish , just that he's not been playing at as high an unbelievable high standard that he was doing a couple of years ago ...in contrast Cronaldo looked to be a dead weight and I presumed that he'd had his best days but he seems to have reinvented himself and of course he's been helped by Zidane making flamin Madrid good again ...