Anti-dr.stonefags, if you go on about "Huh, someone said this would be realistic but there is unrealistic shit," get over it.
>T-the anime has inventions that can actually be made. But there are unrealistic things in the anime. Therefore, the anime lied to me!
No, it didn't. For one thing, it starts right off the bat with everyone in the world being encased in stone, but still being alive, and with a character staying conscious for thousands of years while counting every second and not going insane by this. If you kept watching the anime after such a beginning, you knew there were ingredients that couldn't happen in real life. (Again, it's anime.) If, after that, you still complain about things being unrealistic, then I don't know what to tell you. Other than the problem is your attitude.
The inventions in the anime can actually be made. Though in many cases it would take a lot of failed attempts, and doing it by hand without being a skilled craftsman the finished product would still have flaws. But viewers won't stick around for hundreds of episodes of failed attempts, or watching generations of characters improve on a flawed product. So instead we get the faster route. This, too, is unrealistic. What is realistic is, as mentioned, that you actually can make these inventions - you can make gunpowder, soap, etc, from scratch. Maybe you could enjoy this. Otherwise you're watching the wrong show.
Or, you can take this realism and use it to point out that OTHER parts of the anime are NOT realistic, and claim you were lied to, so you seem smart and above it all. Well. You'll only impress yourself. It's a good story that has already been enjoyed by a lot of people in manga form, and if you can't watch it without having to point out what isn't realistic, then I suggest you either stop watching or get over it.
Don't blame the anime for your lack of brain cells and two digit IQ. Go watch isekaishit or fire force or something else.