The manga talks about this a bit better, but the whole thing with levels is, it isn’t enough you got roughly the material you want to make something. You need it prepared to high purity, specific dimensions, with proper strength, all that thing. And for that you need… well, modern tech. They’ll speed it up because they already know what they want (and how to get it), but even then it’s going to be a lot of work.

Glad Dr. Xeno joined the team though. Otherwise Senku and the gang would be stuck in Pará forever.