Brooks law applies to a late project. However if the project isn't late yet - recognizing it will be and adding the right people now can make a difference in preventing it from becoming late. This is hard: first you need to add the architectures and senior engineers (both are badly needed on some other project that will be late without them) spending a few years getting the right frameworks in place, only then can a bunch of new teams join - you take a hit while they learn the new architecture and framework, but a few months latter they are all getting their part done in near isolation. (note isolation - this implies you have figured out the modules correctly to avoid communication problems - a hard problem in itself)