Any team starting with microservices on an unvalidated concept likely hasn't built a big project from the ground up before

If it's a small engineering team there is nothing more optimal than working on a big scappy vertical codebase in the early stages

In the fortunate situation you need to start scaling -- breaking that out into MS later is usually low effort and fun

If you break it up to early you often end up with logic ghettos forming in the wrong stack that become near impossible to relocate later

I was talking to a startup last year who were hiring several hundred engineers to build a handful of microservice stacks in anticipation of the traffic they may get at launch (success expected because of previous unrelated founder experience), and wanting to make it easier to deploy vast engineering resource on it -- they've still not launched anything