My take is that he has no problem with the club he has a problem with not playing. He's good enough right now to play regularly for a ton of teams and to be sitting on the bench, and sitting behind 1 goal a season wingers, has to frustrate him.
He went on loan because Allardyce wouldn't play him. He wanted to go back because RBL did play him. He got frustrated this year because he wasn't playing again. I see that as the overarching problem not that he hates Everton.
I also think the "he hates Everton" narrative is manufactured. I dont know what the evidence is. You joke about him posting it on Instagram but honestly that would be the first concrete thing on the matter that I can think of. So far it's about how he doesn't smile enough.