Just like with Jamie Lynn Sigler with The Sopranos, everyone figured out that the casting was wrong just a little too late.
Serious question -- what's wrong with her? I liked her on The Sopranos, but can't recall seeing her in anything else.
I don't have strong feelings about her either way. HBO HQ saw footage of her and wanted her out. David Chase wanted her in. So he kept production at a speed where it was too expensive to recast her.
Much of the casting of the Soprano children came rooted from The Godfather legacy. Mario Puzo made Sonny Corleone into almost a "Caucasian" by proxy. His features, as per the novel, were not traditionally Italian. There was a heavy discussion of how the sister, Connie, was not attractive and had unpleasant features associated with being "Italian", and how her husband, Carlo Rizzi, was seen more as an American level of "handsome" archetype. Something to consider is that when Puzo wrote The Godfather, the culture and what was seen as beauty and desirable was different. Also the larger social divide against Italian Americans or any other immigrants into New York during the timeline of the book. Puzo had a lot of resentment and self loathing in all his writing. You'll see hints of that "anti Italian" sentiment brimming in storylines in both GF2 and GF3.
So you'll see that resonate with lots of writers who were inspired by The Godfather. How the children were written and constructed.
One child is classically "American" And if there is another child, that kid is more physically ranged out to the "old country look"
From a practical standpoint, a large production also wants as few minors as possible. Having minors in the main cast causes all kinds of added layers of complexity because they have limited hours they can work ( via SAG) and other limits designed to protect them. This is why Keira Knightley being cast in Pirates Of The Caribbean was such a huge surprise in the media optics world. Because every limitation in filming is time, and that lost time is money. And even with Johnny Depp, period pieces like that, pirates and such, is not something that is a guaranteed blockbuster hit. Sure, Pirates is a huge franchise now. But no one knew that would happen for sure before the first film.
Sigler, at least for Chase, didn't offer the same complicated limitations that Robert Iler did, he was still a minor when the show began ( HBO HQ regretted that casting later as well, Iler's personal problems caused shooting delays, which again cost money)
HBO doesn't really want unprovens and unknowns in their casts. Not in a major role. They want "cost certainty" , as much as possible, it's part of how they operate. David Chase, as of today, can casts whom he wants to cast. But back then, he was still largely just a writer, albeit one with awards cache, and someone who was not proven as a show runner. There were concerns about how Sigler looked ( unfortunate but that's just how it works) and her health considerations were a concern ( not a secret to HBO, not even in the beginning, no matter what anyone says)
Anyone could have played Meadow Soprano. There's nothing Sigler did that really stood out to anyone. She could have been recast and the show would have gone on. Now you couldn't replace Gandolfini and it's difficult to think of someone who could replace Edie Falco. But it's not like all the major parts were untouchable.
HBO HQ didn't like the way she looked. But it's Hollywood, that's part of the game. If you watch TLOU closely, Bella Ramsey's weight fluctuates sometimes from scene to scene and from episode to episode. That's a huge "No No" in the industry. While a shooting schedule could take months and months, the timeline in the show's universe could be hours, days or a week. You can't have characters that look heavy and then thin and then heavy. Because shows are often shot out of order. An actor can shoot a scene for Episode 10 then Episode 4 on the same day. Or be asked to come back months later for "pick up" shooting to fix some issues. This was a point on controversy on Titanic. Where James Cameron kept riding Kate Winslet on her weight. Again, if you watch the film, her weight scales up and down from scene to scene. The biggest nail in the coffin for the issue was Liv Tyler and the Lord Of The Rings. She put on a lot of weight very quickly and her part had to be severely trimmed out in Return Of The King and it caused all kinds of madness and cost. It stripped her of blooming A List status.
Hollywood is one of the few places left in modern society where you can just tell someone to shove off and that they won't get the job because you don't like how they look. Or you think they'll get fat on you. Or they look too ethnic. Or you look too old. Or that teenage boys won't want to have fantasies about you in the dark.
The media optics world crosses over into Hollywood through the crisis management factor. A List talent with a budding major scandal could literally tank a film, and nowadays, an entire franchise. Someone like Tom Hiddleston was and is essentially protected because he was too valuable to the MCU. Otherwise that idiot would literally get gunned down in a parking lot somewhere for the crap he's pulled.
IMHO, Sigler was bad casting because she had no real resume, her health was a threat to the production schedule, there were concerns about weight maintenance and some suits just didn't like how ethnic she looked. Some people have tried to massage it later to make everything sound less brutal, but it's just how it works.