Has there ever been anything originally dismissed as pseudoscience that was later proven to be legit?
There is a tendency for real doctors with backing from Academia or whoever's in charge of deciding how you science to just plain getting it wrong and not realizing it for a long time.
Homeopathy is a good example of this, as it appeared to get great results when it was created during the Bubonic Plague and had such staying power to the point that in the 1800's it was considered a legitimate and mainstream field of medical practice.
Now today we know Homeopathy is nonsense... Remembers New Age Healing is still a thing Okay, those of us with sense know homeopathy is garbage. With the only reason it was getting such wonderful results was because the state of medicine for a long period of time in human history was so god awful that not getting any treatment at all was actually the smarter idea. Since Homeopathy is basically just "No medicine at all", that's exactly what was happening with its success.
Incidentally this is also why the Christian Science movement (Which was neither Christian nor Science) had so many people behind it, people were genuinely living longer from it because it required people to stop smoking at a time when no one knew smoking killed you.
Anyhow. With that in mind, I want to know if there's a case where the exact opposite happened.
Where Scientists got together on a subject, said "Wow, only an idiot would believe this. This clearly does not work, can not work, and is totally impossible."
Only for someone to turn around, throw down research proving that there was no pseudo in this proposed pseudoscience with their finest "Ya know I had to do it 'em" face.
The closest I can think of is how people believed that Germ Theory, the idea that tiny invisible creatures were making us all sick, were the ramblings of a mad man. But that was more a refusal to look at evidence, not having evidence that said "No" that was replaced by better evidence that said "Disregard that, the answer is actually Yes"
Can anyone who sciences for a living instead of merely reading science articles as a hobby and understanding basically only a quarter of them at best tell me if something like that has happened?
There’s a recent one I heard on radiolab podcast. In Chinese medicine there’s this concept of Chi that ebbs and flows throughout all of our body and our organs.
Western science dismissed it for a long time, but we were dumbfounded when a cancer would start somewhere, say the liver and then suddenly start appearing elsewhere like the brain, without harming anything in between.
Well, it turns out, our cell drying process for preparing slides for examination was crushing this tiny little matrix of tubes… that connects everything together. It’s working its way through the scientific process to be considered a new organ.
I was curious to learn more about this, because it sounded interesting, so I googled it. I'm guessing you're talking about the interstitium? There's a lot of criticism of that episode for inaccuracies about the interstitium (known for much longer than the 5 years the episode claims - it's been mainstream since at least the 80s), traditional Chinese medicine (the treatments they mention have been proven to be no more effective than a placebo) and the connection between the two (there's no relation between the interstitium and the lines predicted by chi). Everyone in the discussions I found sounded pretty disappointed in the episode.
Even if it's usually pretty accurate (I don't actually know whether it is), radiolab is not the same thing as the scientific establishment, and this is probably why the OP asked if anyone who does science for a living rather than reading pop science articles could reply.
A real shame, I personally do believe in a force that we can't yet detect that's somehow important for life and conciousness....
I hope one day we find it, till then, I won't lie to anyone. This belief of mine is purely based on conjecture, gut instinct, and experiments I've done using good intentions and duct tape (which is to say, none at all)
Edit: Dear downvoters, I'm not saying for a fact this exists, that science points to it, or anything like that. I'm not trying to spread bullshit.