I've worked at companies with monorepos and it pushed me pretty hard in the opposite direction. My philosophy has been to go through the packaging and dependency process early and often, and split off as many things into their open repo as possible.
I'm a bit scatterbrained on this topic, maybe I should sit down and try to organize my thoughts. Every company I've been at that has used monorepos has fallen into a hell of dependencies where changes break things unpredictably. The other big issue I've seen is companies with monorepos ended up not trusting their engineers. Everyone being able to see everything results in lowest common denominator code, and style fights that would never matter without one big repo.
