He leads the run through Force of will.

Wedge and Biggs are both clearly lacking in confidence after the death of so many comrades where as Luke is getting a helping hand from beyond.

The really experienced pilots have all died.

Luke, Biggs and Wedge are the last gasp of the bases defenses and so it makes sense that the most confident will take charge regardless of his experience.

I never had a problem with that.

I had more of a problem with Lando being in charge of Wedge to be honest.

I can see why Captain Calrissian is piloting the Falcon but surely General Antilles should command the attack?

Imperialscum also fails to acknowledge that Luke practically begs Han to lend his piloting skills to the fight too and he is a criminal that the Rebels have just met, which illustrates how desperate the Rebels are for pilots.