My personal rule is that the new technology stack item needs to either make is possible for me to build something that I couldn't have built without it, or need

My personal rule is that the new technology stack item needs to either make is possible for me to build something that I couldn't have built without it, or needs to provide a productivity boost significant enough to overcome the productivity lost by straying from the more familiar path - even harder for team projects where multiple people need to learn the new component.