Fan: new technology

IT technology is changing with each passing day, how do we consider whether to introduce new technology into the project? For example, 18 years is the year of graphqldl, but should we replace restful with it? Every technology has its application scenarios.
A key point in choosing a technology: New technology reduces the incitement of our projects. Fan is a unit used to measure complexity. For example, one of our systems is 100. The introduction of graphql can reduce the complexity of our system by 20%, but the introduction of new technology itself brings complexity, and graphql itself is more complicated. There is a big difference, so his fanning gave him an estimate of 200, so the introduction of it not only did not reduce the complexity of the project, but also increased its complexity, so if our project is not complicated, there is no need to introduce graphql. So why does facebook use it, because Facebook's project is very complicated, and its fanning may be 10,000~, and graphql can reduce the fanning of its system by 20%. In this way, the complexity brought by the introduction of graphql can be ignored, it reduces the The complexity of the Facebook project.