There's a growing body of evidence in psychology that strongly correlates increasing levels of narcissism with increasing levels of Facebook and Instagram use, which makes perfect deductive sense.
Humans have always been narcissistic. They just used to do it in the church, newspapers, schools or streets. psychology is more or a social engineering, not science. the fundamental aspects of humans have remained the same. people used to use make-up and dress fancy as much as they do today for taking selfies.
I've noticed, particularly with the younger half of society, an increasing belief that they (we?) are always "deserving" something better.
that's called entitlement and I agree.
I'll certainly agree with you there. However, I think technology has made validation easier and easier for some to achieve. Merely the ability to curate the photos we post online allows us to get an inflated sense of self. One is perceived as much more attractive if one only shows the best 1% of their self-curated photos! One's apparent public image can also be crafted by carefully presenting only the socially acceptable hobbies, musical choices, etc. I have observed this effect on Tinder, which provides one microcosmic example.
I'm unaware of an analog for this effect that predates social media and camera-phones. The level of ubiquity was simply not there with personal ads, which seems to be the closest to come immediately to mind.
I think this ends up being bad for everyone. Here's a bit of data you may have already seen:
https://theblog.okcupid.com/your-looks-and-your-inbox-8715c0f1561e
"As you can see from the gray line, women rate an incredible 80% of guys as worse-looking than medium."