[asimpletune]

This is what people always say but it's not really the only case, and it's not even a particularly good case. You could achieve the same organizational thing through modules, for example.

The real—and the one thing you can't replicate—is data isolation.

Of course there are other benefits, but it's data isolation is the differentiator of micro-services and other types of architecture.

[regularfry]

It's not just the modular organisation that you've got to get right though, although that's definitely a big thing. Deployment independence matters too: if I've got a perfectly modular monolith but I have to coordinate with everyone else who lives in that monolith to get my module into production, it's leaving half the gains on the table.

[asimpletune]

That's true too. So, the two things are data isolation and operational independence.