The Unix philosophy references some concrete properties of software (many processes performing small tasks, communicating with text streams), but these are neither desirable (serialize/copy/deserialize is wasteful and kills locality; process boundaries preclude inlining and other optimizations) nor really core to compositionality. The compositionality of processes and pipes is arguably the best thing about Unix, but doesn't even work terribly well: piping n different inputs into the same command requires hacky workarounds, and you end up writing ad-hoc parsers/text-manglers constantly.

One way to cast the ideological stance of the Unix philosophy is "simplicity of implementation at all costs"; the costs include memory unsafety, poor performance (of pipelines and shell scripts), code duplication, race conditions (look at the filesystem, a vast blob of global mutable state!). It's time we start fixing these problems and abandon the mistakes of Unix. Yes, composition is important, but you don't have to sacrifice so terribly much to get it.