I specifically mean trans people, not intersex people, though they have existed too. There are plenty of ancient cultures with evidence of what we would call trans people today, with some even being revered. Sorry to not give sources, but I'm just not invested enough to go research specifics at the moment.
I immediately think of butter, fat, dairy, and eggs. We were all told around the 1980's to avoid them as they will make you obese, raise blood pressure and cholesterol levels. Until pretty recently the American FA was still saying are all bad, then it went to "in moderation" etc. In fact it was all enjoyed and quite healthy up to the late 1970's and now again it is basically back in most people's diets.
Actually, we're discovering, other foods are often the cause of those symptoms, but don't let me knock the advertising industry for fast and processed foods ;-)
Cancel culture. It's been around for a very long time, though it used to be expressed in shunning, banishment, or communal acts of corporeal harm (e.g. tarring and feathering, lynching, etc.)
Edit: just realized the question was for something true, not just something that's been around for longer than people think lol
Nowadays, everybody is trying to talk, like they have something to say. But nothing comes out when they move their lips, just a bunch of gibberish, like they forgot about Dre.
The children now love luxury; they have bad manners, contempt for authority; they show disrespect for elders and love chatter in place of exercise. Children are now tyrants, not the servants of their households. They no longer rise when elders enter the room. They contradict their parents, chatter before company, gobble up dainties at the table, cross their legs, and tyrannize their teachers.
Slightly different tack ... by the time most people recognise a problem, and feel like it's happening "now", the reality is that it started long ago, has been ramping up gradually for a while, but most people didn't want to bother thinking about or doing anything about.
Climate change being kinda obvious. The thing with Google and Chrome lately has been like 10 years in the making at least.
Generally, IME, when something goes wrong even in someone's personal life ... there was something wrong the whole time being ignored. Just recently I spoke to someone about a recently divorced couple who were buying houses and planning long term things months before the divorce. I pointed out that it had to be that way as they were desperately hanging on to the idea that the marriage can work when in reality it had died years before.
The children now love luxury; they have bad manners, contempt for authority; they show disrespect for elders and love chatter in place of exercise. Children are now tyrants, not the servants of their households. They no longer rise when elders enter the room. They contradict their parents, chatter before company, gobble up dainties at the table, cross their legs, and tyrannize their teachers.
Yeah I dunno about this one. Public schools and the middle class have been squeezed pretty hard the past 30 years. The unfortunate events we hear about far too often, seem to keep getting worse. It never occurred or even was something on my radar growing up.
Police reform has like a century of the same rhetoric without actually fixing the problem. You can read about it in old archives, and sounds hauntingly familiar to what you'd read from a modern reformist who opposes abolition