Mappō (a.k.a mòfǎ, mạt pháp) is a term used by the majority of Mahayana Buddhism branches in East and Southeast Asia. It was mentioned in the Mahayana Mahaparinirvaṇa Sutra, signalling the declination of Buddhism and corruption of society as a whole. The sutra painted a grim picture of Buddhism's future, where monks violate the precepts and preach a perverted version of the Buddha's teaching.
Most of the times where this concept is mentioned, it is to achieve political purposes, e.g to gain legitimacy by demonising other people or sects. This has happened since more than a thousand years ago, in ancient China, Japan, Korea, Vietnam, and is still going on.
Personally, I found the concept and its details unhelpful since it gives practitioners (especially beginners) the feeling that the world is falling apart. I'd like know why such description is necessary for Buddhists to know, and what is the optimal way to address it?