In the final battle of Avengers: Endgame, Doctor Strange is pretty much useless, spending almost all of the time holding water up so it doesn't flood the battleground.
Was there any sort of commentary from the directors/film crew as of why they chose to put him aside?
Screenwriter Stephen McFeely touches on the issue in this New York Times interview, answering a question about deciding where in the two movies major events would happen:
Another big plot point is when everyone comes back. So the question is, is it early in the second movie? Late in the second movie? You notice the players left on the board are the O.G. Avengers [Captain America, Iron Man, Thor, the Hulk, Black Widow and Hawkeye], and let’s give them their due. It meant that we were likely going to bring people back late. So that if you were a big fan of Doctor Strange or Black Panther or Bucky [the Winter Soldier] or Sam [the Falcon], you’re only going to get a little brief window on them. It can’t be all things to all people.
And later answering a question about Captain Marvel's role:
Certainly, Captain Marvel is in [“Endgame”] a little less than you would have thought. But that’s not the story we’re trying to tell — it’s the original Avengers dealing with loss and coming to a conclusion, and she’s the new, fresh blood.
The newer members of the team whose powers could conceivably win the battle almost single-handedly -- Dr. Strange, Scarlet Witch, Captain Marvel -- weren't supposed to overshadow the original Avengers.
But Dr. Strange has played a key role:
Stark: Hey. You said one out of 14 million, we win, yeah? Tell me this is it.
Strange: If I tell you what happens, it won't happen.
"What happens" being that Tony must sacrifice himself by using the Infinity Stones.
I'm going to frame challenge your question and state that he had the one of the most important roles to play during the battle. As such he wasn't removed from the battle he was a vital part of it.
Strange was the one who went around and gathered up all of the Avengers and their allies to fight Thanos and his army. Had Strange not been around to do that Thanos would easily have beaten the Avengers.
PETER PARKER: Hey! Holy cow. You will not believe what's been going on. Do you remember when we were in space? And I got all dusty? I must've passed out, 'cause I woke up, and you were gone.But Doctor Strange was there, right? He was like, "It's been five years. Come on, they need us!" And then he started doing the yellow sparkly thing that he does all the time...
Avengers: Endgame
He then holds back the water and had that not happened the battlefield would have been swept through making many allied forces useless, injuring and killing others. He played a vital role in making sure things went smoothly for the team.
Lastly, he holds up the "1" finger for Tony which no matter how you look at it prompted Tony to act and sacrifice himself.
Without Strange and his actions the Avengers would have lost before the battle even began. He might not have done much fighting but he did stuff that was a lot more useful than that.
There are no official answers, only in-universe explanations, which is that:
Strange saw one outcome where they win, him holding up that water is part of it.
In Avengers: Infinity War, Strange tells Iron man that he saw more than 14 million possible future outcomes, and in only of them they win.
So, in the one outcome where they win, he probably saw what his role had to be in the final battle, that being holding up that water so it doesn't flood the battlefield.
