In a system structured on microservices, each team is able to perform most of the tasks on their own, independently from other teams. Designing the services so that they are as independent as possible and with minimal dependencies is key to achieving a good development speed.
Therefore, microservice separation allows teams to work independently and in parallel, while with monoliths, most of the people working on it keep track of what goes on, even to the point of being distracted with work out of the field of focus of a particular developer. They'll know when a new version is released and see new code being added to the same code base they are working on. However, that's not the case in the microservices architecture. Here, teams focus on their services and are not distracted by other features. This brings clarity and productivity...