I've shifted to focusing on repo == team. If your organizational structure is to have many little teams that are independent from each other, then you build your source code management to reflect that.

I built my engineering staff to focus on any of the initiatives that my boss hands to me (changes week/week) - so we went monorepo so we could move between those projects/apps/programs quickly.

We knew that we didn't want to pay the maintenance cost just because microservices/multirepo was a buzzword AND we wanted future ventures to get faster (example: we solved identity for authn/authz once and now every app that needs it after can leverage it and we can upgrade identity and all of its consumers in one pull request).