[heavenlyhash]

I think I'd more or less agree with that.

For example, one of the questions I generally ask in a meeting room that's considering this topic, and has for example microservices in flight, is: "Are you willing to put in the work to make Service A support more than one version at a time in Service B?", and if not, then that's a very (very) strong indicator that the level of coupling and lack of organizational boundaries will result in pain from anything but a monorepo.

I prefer to split things up when possible. When it does fit, there's many benefits. There's also the concern that building too much culture and tooling that presumes a lack of splitting of repos can become its own form of trap which becomes increasingly hard to navigate out of, even if you later want to, as the situation self-iterates. But I agree that splitting things out needs justification, and the "default" stance should include that.