I honestly couldn't give a shite how shiny, new or aesthetically pleasing Old Trafford looks or how many flippin corporate boxes there are. I was always annoyed how happy so many United fans were to do away with things like naming rights to Old Trafford just for some extra money. But now apparently we need to knock down the whole place and build a great new glass bowl with world class jacks, amazing legroom and an endless amount of box seats for monied yuppies. Seriously, no thanks.
There are certain circumstances were rebuilds or new grounds are necessary. Highbury was tiny for a club of Arsenal's size, the same goes for Spurs and West Ham. Why do United need to do this? They already have the biggest club ground in the country with room to expand. The main reason I'm always so adverse to needless new stadiums in modern sports is that they're rarely done for the fan's benefit. My Detroit Red Wings are moving to a new arena this year, playing since '79 at Joe Louis Arena. All the build up to the new place has been fans talking about how much of a 'dump' the old place was and the glittering palace that the new place is going to be. Lo and behold the true nature of modern sports franchises. The new arena has a shít corporate name with it's logo smeared everywhere, it houses a smaller capacity with increased box seat capacity along with some gimmicky 'gondola' seats hanging from the roof. The Joe may well have been a 'dump', made of plain white concrete, no glamour or glass facade, no neon lights to blind you everywhere but it had a soul, was the site of one the team's greatest eras and was named after an icon of the city.
What's shocking is that even though it only opened in 1979 it was the second oldest arena in the NHL after Madison Square Garden. This is the route American sports has been going for decades, so over saturated by corporate sponsors, endless TV adverts and 'state of the art' arenas with no personality. Only a few holdouts remain like Fenway, Lambeau and Soldier. I'd utterly hate United to go down that route. They have a famous stadium that's stood at the same place for over a century, been destroyed during WW2 and rebuilt and has showcased so many famous moments throughout the club's history. Expand it, 'refurbish' if you must, but the day it's knocked down in favour of some Emirates clone is one I really hope I don't get to see.
Hoping for a new stadium to improve crowd atmosphere or fan engagement is a fool's errand. There are only a few examples of modern arenas achieving this (Montreal's Bell Centre is one, but a very unique case for that organisation).
TLDR; Old Trafford is fine the way is is, there isn't another place that looks like it, quirky as it is.