It’s not that reductionism is wrong, but rather that it’s only part of the story. Additional understanding can be gleaned through a bottom-up, emergent explanation which is orthogonal to the top-down reductionist explanation of the same system.
It is important to take seriously the reality of higher level models (maps). Or alternatively to admit that they are just as unreal, but also just as important to understanding, as the lower level models. As Aaron Boyden points out, it is not a foregone conclusion that there is a most basic level.
From the Wikipedia definition for “reductionism”:
“Reductionism can either mean (a) an approach to understanding the nature of complex things by reducing them to the interactions of their parts, or to simpler or more fundamental things or (b) a philosophical position that a complex system is nothing but the sum of its parts, and that an account of it can be reduced to accounts of individual constituents.”
and
“The limit of reductionism’s usefulness stems from emergent properties of complex systems which are more common at certain levels of organization.”