I think its abandonment is related to the adoption of agile methodologies. UML was used to describe systems from day one. Agile methodologies came in, claiming that we don’t need it.

You still need to describe systems in agile.

All agile does is ask you to iterate, which means updating your design, your code, and your tests & documentation, as you learn.

Please read the agile manifesto again, and actually apply it. It does not say we don’t do design at all. Never did.