In 1900, people predicted we would not fly for another 1000 years. Yet in 1903 we had the first manned flight and 66 years later-we went to the moon. These things were much more doable than we thought but it is 2026 and we still do not have a cure for baldness or a reliable male birth control pill.

What are some other examples? Stuff like FTL and anti-gravity don’t count as they might be inherently impossible

Commercial utility-scale fusion power generation.

- Cloning mammals. Dolly the sheep was a bit of a surprise.
- Gene editing (CRISPR etc.). Still early days, but I doubt Watson, Crick, or Pauling ever thought it would happen so soon.
- Rapid, low cost DNA sequencing. Francis Collins didn't expect Craig Venter to do it that way.
- Photograph of a black hole.
- The www. It all started as a DoD and University thing, then it went commercial and changed the world.

Razorback Gorilla said:

In 1900, people predicted we would not fly for another 1000 years. Yet in 1903 we had the first manned flight and 66 years later-we went to the moon. These things were much more doable than we thought but it is 2026 and we still do not have a cure for baldness or a reliable male birth control pill.

What are some other examples? Stuff like FTL and anti-gravity don’t count as they might be inherently impossible

You seem to be asking for things that will turn out to be much easier to do than is expected, not harder. That's the opposite of the title. Well, I don't know. Unexpected breakthroughs are totally unpredictable.

The biggest breakthrough by far in my 71 years of life occurred in 2016 when an AI defeated Lee Sedol to become the Go champion of the world. Go can't be solved by brute force so it was a major breakthough I had not expected in my lifetime. Since then it has all progressed much faster than I ever would have thought possible. It appears Mr. Kurzweil was right, AI is accelerating its own progress.

I was further astounded when AI was able to make music better than humans can do. While you would expect AI singing to be robotic, it's MORE expressive and feeling than humans can do. Amazing. I've learned that the way to tell it's AI is that the singer sounds too good to be true. I would have thought this would have been one of the hardest things to do. Instead it seems to have been one of the easier things.

The only other big breakthrough might have been the 1947 invention of the transistor. This transformed society but much more slowly than AI. I wasn't around at the time so I don't know whether or not it was unexpected.

While Rogaine isn't a cure for baldness I'm told it is a successful preventative therapy.