At present, in what aspects is Julia still relatively weak compared to other mainstream programming languages?

Let’s take the discussion on DelaunayTriangulation.jl to Ongoing maintenance and support for DelaunayTriangulation.jl, and keep LoopVectorization.jl in Why is LoopVectorization deprecated?.

It’s not always easy to split threads like these, so if there are other concrete threads like this I encourage folks to start dedicated topics.