The problem with the character of Maria is that she's so sweet and there's really nowhere to go with the character. Maria von Trapp was quoted as saying that she told both Mary Martin and Julie Andrews to "butch it up" (Okay maybe she didn't say it that way, but you get the meaning).
The problem with Luker was that she, imo, is a bland actress and playing a sweet character made her fade into the scenery.
And even Patti Cohenour, who I enjoy, really didn't have the gravitas to play the Mother Superior. I felt like I was watching a high school girl trying to play old and wise.
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.