[lord_jim]

CoffeeScript. It had its time but it's focus on syntax failed to address much of what makes JavaScript difficult to work with.

jquery UI. Jquery still has some use in banging out a quick page but it too is no longer essential

Also possibly Bootstrap. What the hell is going on with development there?

[tannhaeuser]

About Bootstrap: I, too, have questioned the viability of grid frameworks and CSS preprocessors here when we have CSS grids and variables, but I think Bootstrap is such a useful thing for a split designer/developer workflow that it'll live on and eventually converge into using CSS grid directly in a couple years.

Bootstrap team has made slow but steady progress over the last few weekends and is working on documentation issues, so it looks like a new release is imminent.

Update: https://news.ycombinator.com/item?id=14926640