Anduin’s return makes absolutely no sense to me. He appeared randomly in the trailer without much explanation. Choice of other characters make some sense. Thrall and his connection to the planet as a shaman. Moira/Dagran find a new Dwarven kingdom. Alleria playing tag with Xal’atath. Thrall says they need his light, but he has lost his powers. Putting him under even more pressure doesn’t seem to speed up healing.
Does it say anywhere in the story why we need him there?
I’ve been wondering this as well, if I had to guess he’ll tie into the stuff with the Arathi humans, given he’s human, royalty, and a wielder of the light.
Because pushing humans in our faces is the only story Blizzard is capable of writing.
No one knew about the hidden Human kingdom until we went underground so that can’t be his motivation. From a timeline perspective, it doesn’t make sense. Anduin currently doesn’t control Light. If they wanted someone with that power, Liadrin, Turalyon or even Velen would be better suited to this role. Maybe if they mentioned a vision from Azeroth in which they saw Anduin, it would explain his presence, but I don’t think we have anything like that
Because the average WoW player is a middle-aged man with unkept hair/beard, so Anduin makes for the most relatable protagonist over, say, a weird voodoo monster or a weird talking cow.
From a story perspective, it should be pretty obvious. How many times must it be said that “War Within” is both literal and metaphorical? It’s the war within the World-Soul and the war within the characters. SL ending set-up Anduin as a deeply-conflicted individual, who makes sense to feature in this expansion.
In universe, he heard the Radiant song and went after it and thats why he is following us. His friends and close people also want to help him and bring him back to ruling Stormwind.
In a story telling sense, It is another episode of his character arc, this is also an expansion focused on internal development and seems like the perfect time to address every issue with his self doubt.
Watsonian answer: He felt the call of the Radiant song, and being a son of privilege on his gap years, had nothing better to do than follow it.
Doyalist answer: A former story dev who would have been heavily involved in writing TWW has been on the record about pushing hard for Anduin to have the spotlight.
He was Golden’s favorite and a favorite of Blizz in general.
I don’t think appearance matters in this case. And Anduin relatable? People didn’t like his naive approach to the war in BFA. Also he’s most likely the flawless npc in the game
Almost every character can be put into his place as an internally conflicted person. Jaina, Turalyon, Thrall, Calia, Alexstrasza, Nozdormu, Tyrande, Baine and others…
Anduin’s return would make more sense when we focus on Stormwind and Scarlets, not in Expansion about a journey to the heart of the earth
Sorry I was meaning that as more of a meta doylist reason as to why he is in the story.
Conspiracy Theory!
Anduin’s coming back now, so that he’ll head off to Avaloren and join the Arathi Empire. Then, once TLT is over, we are attacked by the Empire! Anduin, having completely lost himself to the Light, becomes a raid boss and dies to our blades.
I like Anduin, he’s the only attempt at writing a more interesting human character in WOW since Arthas. I used to hate him, but now I see the merit of the character. And since the cinematic of TWW and Anduin’s short story, he’s grown on me enormously, I’m rooting for him now.
He needed this time gap, as SL has tarnished his image enormously. he just needs to accept that he is a paladin, as it doesn’t make any sense for him to be a priest who carries a two-handed weapon and wears plate armor.
In fact, now I realize that I never really hated Anduin, I hated the state of the lore until SL, I think Anduin and Sylvanas represented that, hence the hatred directed at the characters.
Because he’s one of the first people that the Vision spoke to, which means he’s got as yet unexplained connection to what’s going on.
I suspect the divine bell effect on his bones has potential. Perfect for the “war within” theme if he can produce Sha. 
The writers decided to make him the lead character. So everything has be be about him.
My suspicion is Metzen has a desire to repair as much damage as Shadowlands did as possible short of blatant recons, which means he needs some of the important characters of that expansion to work past things and move into the current story era.
Seems to be doing the same thing with Thrall, really.
Shadowlands didn’t do any damage. that was Bfa. All what SL did was explore the cosmic force of death to a greater extent.
I thought it was strong independent body type 2’s.
Look at you shilling for Shadowlands just because Slayqueen Suevanas was the main character. Hilarious. 
Since WOW vanilla humans always get the spotlight. In reality human story should have been over when the old alliance was destroyed. All other races are more intresting then them