While 介入 (jièrù) is a functional term, its usage touches on important cultural norms regarding involvement in others' affairs. In many Western cultures, “getting involved” can be seen as a proactive and positive civic duty. In contrast, Chinese culture often places a higher value on respecting boundaries and not involving oneself in situations that are not one's direct responsibility. This is why 介入 (jièrù) often carries a formal weight. It implies that the person or entity intervening has a legitimate reason or authority to do so (e.g., a doctor, a court, a designated mediator). Unsolicited involvement is more likely to be described with the negative term 干涉 (gānshè) (to meddle). On a grand scale, this is reflected in China's long-standing foreign policy of “non-interventionism” (不干涉主义 bù gānshè zhǔyì), which opposes one country's 介入 in the internal affairs of another. Therefore, using 介入 (jièrù) correctly shows an understanding of social and political boundaries.
介入 (jièrù) is common in formal and semi-formal contexts. You'll frequently encounter it in news, academic discussions, and professional settings.
The biggest pitfall for learners is confusing 介入 (jièrù) with similar-sounding concepts.