It boils down to focus. When you present skills/experience that aren't relevant to what someone is hiring for, it distracts from your main message ("I can do th

It boils down to focus. When you present skills/experience that aren't relevant to what someone is hiring for, it distracts from your main message ("I can do this job well, pls hire") and leaves your audience unsure of what you'd be a good fit for. A fullstack developer on the job hunt should have versions of his/her resume that are tailored for front end, back end, and fullstack. The front end and back end resumes should demonstrate a clear focus on the relevant responsibilities. That's not to say he/she should lie or exaggerate. All it takes is leaving off the impressive experience/skills that aren't relevant. It seems counter intuitive, but the idea is to present oneself as a specialist. For whatever reason, people are suspicious when others claim to be skilled at multiple things