I am not in the Millenial set, and don't even have an Instagram account lol, but I think this is a good pairing in respect to the goal to revitalize
Coach.
Even as a stodgy Gen Xer, until the last couple years I often found the Coach line a bit too "safe" for me - I recognized the boutique line had lovely leathers and such, but many of the styles to me were, while not necessarily
too mature, just not quite fun enough. I find - when it comes to handbags at least - I often am drawn to a balance: work friendly/easy-wearing but with a personality twist. Sure, some days I carry something more safe, but a bag for me is a chance to express a bit of personality in a not-too-in-your-face way (because I am just not an in-your-face person myself). I have liked, for example, Kate Spade's less over the top whimsy (I have no interest in a taco truck bag or carrying around a straw camel, for example, but put a subtle bow on a bag - sure!). I don't consider myself very girly (you will not catch me carrying a pink bag!) but I like those little twists.
I love that Coach has moved towards adding a more mature whimsy in designs - like the patchwork or whipstitching in Rogues, the tea roses, the upcoming kisslock doctor bags, the dino charms, the detailed patterns, and even the colour combinations. While there are some I still would never carry or "pull off" I definitely appreciate the designs and I suppose, the "artistic vision".
I also think that some of these are things that can easily translate to younger crowds - I have a few younger acquaintances who have expressed they love, for example, the space collection; while that collection does not appeal to me personally, it seems to hit a chord with a few of them. Buf it you asked them about Coach a year or two ago, they would have wrinkled their noses!
I think the pairing is a great way to appeal and market to the younger generations who so far might not be that interested in accessories, bags and so on (I did not really get interested myself in bags until I was approaching 30 - and of course part of that was not having the income to spend much on what I viewed as something larger just to carry my smaller wallet!) but might turn their eye that way if they see one of their favoured celebrities wearing it - and while I know little of Selena Gomez, I have seen her carrying/wearing Coach quite a bit. And, if as I said before, they also see those bags (and accessories, t-shirts, dresses) as ways to express something that hits a chord for them.
It is great that it seems mutually beneficial - Coach/Vevers gets the marketing channel to younger generations and her fanbase, and Selena seems to be getting some benefit when it comes to her philanthropic ventures.
ETA: the campaign photos seem um, inspired by prior campaigns though. Same/similar poses in same/similar location/prop...just different "model" and colour bag.