There have been tons of studies surrounding the "toxic" culture surrounding Instagram. While it shouldn't come as a surprise to anyone that a social media network that was solely created for sharing appealing pictures are inherently "shallow" and focus on finding that "perfect shot", this has helped to foster some unrealistic expectations that folks, especially impressionable young people, find it nearly impossible to live up to, creating inferiority complexes as a result.
The obsession to satisfy the appearance of being successful, skilled, passionate, sensual, adventurous, etc. becomes more important than actually fulfilling what those traits mean for an individual on a personal level. I.e., folks are just doing it for the 'gram and once it's "successful" there, that's usually the end result they're going for.
While there are plenty of people snapping epic looking shots on vacations in beautiful places they ultimately spend toying away on their phone the whole time they're there, this 'gram beauty mentality can be perfectly embodied by the photos that people snap of themselves. Makeup that's perfected for a specific photo session, or heck, depending on how much money you have, cosmetic surgery to appear aesthetically pleasing in photographs and short single-expression videos, but kind of monstrous in real life.
This phenomenon can be thoroughly summed up in a popular rallying cry, uniting those who may be intimidated by the impossible supposed beauty of folks on social media with a singular chorus of: "you're not ugly, you're just broke."
No one's accusing the celebrities in these older photos of not being aesthetically pleasing, however, there's a marked difference, due to a combination of time, an ability to afford better stylists, new health/wellness regimes, or maybe a little bit of cosmetic surgery, that's helped transform the way they look.