What if Denis Papin hadn't invented the piston steam engine?

One of the unsung heroes of modern technology is, I think, Denis Papin. https://en.wikipedia.org/wiki/Denis_Papin Papin was the inventor of the first piston steam engine. And the piston is really the basis of both the steam engine, and the internal combustion engine and, hence, of the entire revolution in transportation technology and engineering in the nineteenth and twentieth centuries. It is, of course well known that the Romans invented the steam engine in the second century A.D., and made a variety of simple steam toy mechanisms employing it. It is also well known that it took another 1500 years before the steam engine had any practical application. Quite specifically, it wasn't until Denis Papin invented the piston steam engine, that the steam engine really took off as a practical reality. While there a number of explanations as to why it took so long for human civilization to take advantage of the potential of steam power -- the lack high quality iron and steel, the lack of blast furnaces -- the Romans were extremely skilled engineers -- aqueducts, superb roads, the Pantheon and the arch -- and these conventional explanations don't seem to quite cover the case. However, the concept of the piston steam engine -- powering a mechanism using a perfect vacuum -- is rather a long conceptual stretch for a Roman engineer, I believe. And this long conceptual stretch, the fact that the Romans didn't even possess the concept of a perfect vacuum, which was systematically developed during the middle ages and the Renaissance, is likely the problem here. https://en.wikipedia.org/wiki/Vacuum Now, one could argue here, of course, that, given that Papin had the concept of a perfect vacuum by the late seventeenth century, the development of the piston steam engine was largely inevitable here. So, instead, we could simply consider, 'what if the concept of a vacuum had never been developed?', in terms of modern technology. In any case, I would argue that, without the concept of vacuum engines, and the piston, we're still back in the seventeenth century, or, pretty close to it. There is very little technological progress, or social progress in terms of life expectancy or standard of living, in the succeeding centuries. Thoughts?