Reinvention:
Suddenly it was cool to play it, but only to play it the new way. The old-schoolers were not often embraced as its pioneers and teachers so much as ignored.
One is only a "pioneer" so long as you are exploring new territory - if you come to rest in a space you find comfortable, you become settled, then a traditionalist. And if you've settled in, you limit what you have to teach future generations of gamers about. And if that's not an experience they are interested in, yeah, you slide into obsolescence.
Don't kid yourself - this is basic to generational change, not RPGs, specifically.
By the way - I started playing RPGs in the early 80s. I would be an "old-schooler", except I didn't settle in on one game or style.
The original generations who grew up on RPGs through the 70s 80s 90s had a unity
This is inaccurate. We didn't have unity - before the internet we just didn't have sufficient communication among us to recognize that there were lots of different approaches to gaming that had already developed. It became even less accurate when the World of Darkness came along in the early 90s, and made it clear how many RPG players had much different ideas about what playing as about.
... they did not care about political differences or socio-economic differences.
Upon what do you base this assertion?
In the very early days, RPGs were dominated by white guys. They weren't egalitarian enough to change that. It isn't that they did not care about these matters - their tables were not diverse enough for their attitudes to be challenged much.
They set all that aside and connected through the shared passion of the game
No. Factually incorrect. The gamers of the 70s and 80s were not somehow better than the rest of the world around them. RPG players are not, broadly, exceptional in our attitudes or behaviors - gamers are generally as bad as everyone else, and always have been. So, gamers of the 70s were generally as racist and sexist and -phobic as the 70s, and so on. And their tables showed it.
No. The original Nerds were bulk-dumped by the new kids who think the old boys racist because they are heterosexual males and kill imaginary green-skins.
That's not what happened. Culture changes over time, from one generation to the next. And, as always, not all the people come along as the culture around them changes. They were not "bulk-dumped". They didn't choose to come along.
The rebranded products now published by an industry which cares more about profit and image than it does about the people who fund it.
Oh, please. TSR had the moniker "T$R" for a reason - companies all care about profit. It is just nowadays they know a whole lot more about the business of RPGs and about the market of players than TSR ever did. They learned more than their forebears knew. Go figure!
We are all doing this because we are dysfunctional as a collective.
No, we have never really been one collective. That's a rosy retrospective fiction.