The (lack of) time aspect is something all of these novels share. Since all of these novels share the same flaw, they all break my experience reading them in a similar manner, and I lump them all together. As to why I say time is so important: I'm an engineer and have had a diverse selection of courses early on in college, chemistry, physics, mechanics etc. before specializing and then going on to work. If you put me in a world like that, I can explain basic scientific concepts, teach them the correct mindset to do science and teach them theories like Newton's gravitational theory, mechanics, basic chemistry and so on. What I cannot do is set up a huge variety of experiments, build or even make plans/schematic of the necessary tools, redo and tweak all of these experiments to get the desired results, confirm the results and prototype applications, get the working prototypes to a point where they reach the (e.g. efficiency) requirements, scale the prototypes up for deployment in e.g. a factory, and so on. There's a lot of nooks and crannies in technological development past the purely theoretical. The use of having one modern engineer in an old society is actually ... surprisingly little. All these nooks and crannies were explored in the past by a large amount of scientists over the past hundreds of years. While science 100 years ago doesn't compare to science now in terms of knowledge volume, don't underestimate the amount of steps and amount of theoretical/practical knowledge. Additionally, knowledge of materials (which eventually evolved into material science) changed quite a bit from the middle ages to 100 years ago. In short, it's too much, with too little resources, in waaaaay too little time. Tales of the Reincarnated Lord solves this problem - by introducing less technology. Mechanics and gunpowder are from what I remember all that's involved, which makes it a lot easier to swallow that first of all he knows these things, theoretically and practically, and second that he's able to get these technologies in use. Additionally, there's a lot more delegation involved in order to grow something of a scientific community. It's still a bit ridiculous if I think about it, but it doesn't break my immersion.