MGC will last longer than Raf Simons at Dior. I think her contract was set up so that it would be longer than Raf's, as Dior does not want to have another new creative director after 3 years of having a new designer again. While getting a new designer is good for creating temporary hype, it can have detrimental effects if the house acts like a revolving door. The top job becomes the job that no one wants to keep.
The question about what makes a Dior bag distinctly Dior? It's the Cannage quilting, Dior charms, curved lady-like top handles, and a couture approach to embellishment. The reissued vintage bags are definitely Dior. Bags that don't have these traits may not look like they are distinctly Dior, but if you look at most brands, you can say pretty much the same thing about some of their styles. Take away the logo, and bags like Chanel's Cerf tote, Prada Galleria, Vuitton Neverfull/Goyard St. Louis, and Gucci Soho could technically belong to any brand with nothing truly distinctive.
In other words, this is a dilemma for every brand that has multiple bag offerings, not just Dior.
@TraceySH the fact that her Dior was more exciting for you means that her re-branding is successful, and many woman share your experience. Her Dior is commercially successful, is resonating with a larger age-group (with pieces that appeal to very young clients as well as mature clients), and I see her staying power at the house.