While cut is important, it can be more of a preference. I tend to focus more on color and clarity.
Like
@papertiger said, the only thing I'd be concerned with is a cut that hides flaws.
But there are some places that tend to do a more shallow or deep cut depending on how they want the diamond to look. For example, Tiffany cuts their diamonds in a way to maximize their brilliance and sparkle. Therefore, they cut their diamonds a little more shallow than the ideal range for a diamond. This means that most of their cuts isn't "ideal" according to GIA standards but that's not what is important to them.
(This is probably also why they have their own labs and grading system
).
However, this does not deter many people, including me, from buying Tiffany diamonds.
Here's an article about Tiffany diamonds if you want to get a little nerdy lol
https://niceice.com/online-diamond-vendors/tiffany-diamonds/