Not sure how much of it is Jota/the team around him - Jota wasn't looking like he'd turn out like he has, we wouldn't have accepted £45m for him otherwise - but for Raul the ratio of bad games to good was already starting to tip in the wrong direction in the second half of that 19/20 season.
I say "slow and steady" because it's not like he became ineffectual overnight, but if you could chart his impact on games the line of best fit would be on the same trajectory pre-injury as before. It's felt like he's become a little bit less of the player he was, month by month, for the last two years at least.