Hah, well what was the rate of progress on breeding faster horses vs. internal combustion in the late 19th century? I don't imagine that the progress rate was very high for horses..
I think that that's a better technology comparison because internal combustion was able to leverage the theoretical insights originally derived for steam. There's no shoulders-of-giants effect going on for nuclear fusion, as there wasn't for steam.
The Watt design is when we finally saw steam engines replace animal power in the late 1770s. So not quite 100 years.
But yes, ICE development benefited from all the problems solved by steam power generation. I believe the ability to machine pistons to an accuracy of 0.1" wasn't developed until around 1750. Prior to that, people just hammered iron roundish and called it a day. Good enough for large steam engines, but not too valuable with an ICE.
Fusion seems a good illustration of this. Work started on it about half a century ago. Its motivation was "fission will be cheap, but uranium will get scarce, so let's build fusion reactors that have cheap fuel!" Except fission didn't get cheap, the cost turned out to be dominated by the cost of the power plant, not the fuel, and fusion reactors don't solve that problem AT ALL.