Probably works OK for a small project with a close knit team of skilled contributors where there's some well defined structure and everyone has sufficient high level understanding of that structure to know what kinds of dependencies are or are not healthy to have.

But, unless you have some way of enforcing that access between different components happens through some kind of well defined interfaces, the codebase may end up very tightly coupled and expensive or impractical to evolve and change, if shared memory makes it easy for folks to add direct dependencies between data structures of different components that shouldn't be coupled.