The monolith first approach has always served me well. Nascent projects benefit from portability because they need higher amounts of flux. As they mature let's assume they grow in scale and integrations and somewhere along the line it becomes sensible to break off pieces into services.

To me the big benefit of microservices is scaling out components into flexible independent release cadences but the trouble comes with employing them too early.

https://martinfowler.com/bliki/MonolithFirst.html