She was out of place and unnecessary.
You already had akbar and leia. To kill off akbar so dismisvly immediately made me hostile to the character and sliding leia into the background put me off as well.
Then there is the fact she lacked any sort of military discipline or military competence. The audience had zero reason to trust her.
You just killed off ackbar and Leia then bring in a new character that doesn't act or look like admiral? Military officers in combat dont wear long fancy dresses , its dangrous.
She maybe would of worked as a senator like mon mothma.
At the very least they could of stuck her in a practical military style uniform.
While I can accept most of the criticisms here, one thing to remember is that these are people on the run. We don't know what Holdo was doing when she joined the fleet. Perhaps she was attending some sort of a state function and didn't have time to get into uniform. I got the impression that since Poe was unfamiliar with Holdo, I don't think she was stationed with the crew on D'Qar. She may have been contacted by Leia to rush to join them arriving right before the First Order did and just didn't have time to get into uniform. Its speculation, sure. But we're on a Star Trek board. Our fandom has been trying to connect the disparate dots since 1966!