I volunteered to teach a class on Heron of Alexandria (aka Mechanikos).
The oldest copy of one of his books is from the 16th century and it’s housed at Oxford. He sounds like a prime candidate for people attributing something to a bygone age to make it sound cooler. None of his machines still exist. He writes about optics and steam and vacuums, and from my college classes I associate those topics with 16th century research. At least the Archimedes screw definitely existed in ancient times, but that's not attributed to Heron of Alexandria. His works were popular and shared around, and yet weren't rediscovered until 16th-18th centuries. His Latin is written simply and clearly, and he doesn't ramble on like everyone else in the ancient world.
The Temple to Artemis at Ephesus was already five centuries old when Heron’s automatic door system was (maybe) added to it? Just a History Channel documentary says so. Websites about the temple don’t say so. At least, none of the ones that I've found so far. And it sounds like builders would have had to dig into the marshy ground under the temple to install Heron's device for the doors - maybe not impossible, but really hard to do?
I'm not an expert on the ancient world. People have made references to the aeolipile not being used to create a steam engine because there was a lot of slave labor, and attributed a quote about that to "the emperor." Something like, "Why should we use steam power when we have all of these slaves?" Which emperor? Or is it just a meme and not a quote at all? Besides, it still would have made sense to use the aeolipile and slavery too.
I'm continuing to look for information so please don't just do a quick Google search and post me a link to it, or point me to the History Channel documentary because I've already seen it. I just thought I'd ask the experts here and see if I got any response.
Heron comes up regularly as a question. It would have been quite hard for the Greeks to make his aeolipile do any real work: the technical problems I described here, . The idea that the Greeks didn't bother with technology because they had slaves is discussed here, with u/XenophonTheAthenian correcting my previous assumption that it came from Toynbee. It was much earlier.
As to whether anyone in the ancient world described any of Heron's devices actually being built is perhaps question for a real classicist, but I have never read of it. I would assume that, since it would be really wonderful if it had happened, that ancient source would have been often cited and well-known if it existed. But, when I read about any classical source, it seems like it's quite normal be described as something like " two of the original 20 volumes survive", or "known only in fragments", or "known only as quotations in other works". So perhaps someone did try to build one or more of these devices , and the account has vanished.
There's also a very long history of people drawing cool gizmos on paper/parchment that don't get built or even noticed for quite some time. If they stayed on paper it didn't matter whether they ever could be built, whether some could work and some couldn't. Villard de Honnecourt also put down some fun machines in his sketchbook, in 13th c. France, that were apparently never built. And, like Heron's ,some of them ( like his perpetual motion machine) couldn't have been. Leonardo Da Vinci would do the same thing: his iron pyrite fire-starter seems workable. ( he may have only been the first to draw it; it was the basis for wheellock ignition in guns. ) But his flying machines of course could not fly.
Heron's aeolipile attracted the interest of Sir Charles Parsons, early in his engineering career. He was intrigued by the possibilities, but he also knew something about steam and machine tooling and physics that the Greeks didn't. So, he was able to make one ( size unspecified) with modern materials and tight tolerances, relatively modern bearings and seals, and then stuck it in a cast iron box which he then likely connected to the condenser and air pump of a regular steam engine. Supplied with 100 psi steam ( from what must have been a pretty big boiler) , and rotating in 27 inches of vacuum ( which is pretty low) it spun at 5,000 RPM , and produced 20 horsepower. And used only 40 pounds of steam per horsepower per hour, which really wasn't bad for any steam engine of the later 19th c. Parsons would go on to develop the first really practical steam turbines.