How Dylan SHOULD have returned
Dylan returned and was a pathetic druggy stalker always clamming for Kelly. He degressed rather than progressed as a character. After Toni's death and his time away he should have come back stronger. Here's how he should have returned:
Not at an underwhelming awkward Thanksgiving event but some kind of epic return as part of a season finale
He should have been an enigma type figure who returned to provide guidance to his friends in the final seasons
He should have been an inspirational figure gaining wisdom over the years. Maybe he did lots of soul searching and therapy over the 3 years. His goal was then to share this wisdom with his friends.
He should NOT have pinned for Kelly but instead be the best friend he could be for her. Brandon should have been Kelly's end game and Dylan himself should have advocated for that.
Basically his role would be to show up to help his friends when a problem arose and then "mysteriously vanish' until the next problem arrives. Sounds weird at first but if you think about he is sort of acting like a guardian angel. An even more weird twist would be something like a Sixth Sense twist where he appears to help but actually he's an angel and it's revealed he was dead all along! I dunno maybe that's a bit too much but at minimum he should have returned with the aim to guide characters to happiness until the season finale and then he would ride off into the sunset selflessly.