I do love Dart, though I don't think it would be useful to add it to the list. Dart, though being a general-purpose programming language, is largely geared towards building apps and therefore has a relatively small standard library for doing math, vectors, sorting, and so on. Standard input/output is also slower; it does have streams to more efficiently read I/O, but there's no good built-in way to achieve this and requires some manual (and perhaps tedious) assistance from the programmer. Even Go does better than that.

Plus even though its speed has improved quite a lot since AOT compilation was added around Dart 2.6 (see the dart-sass vs libsass benchmark, which is a bit like comparing Dart against C++ in single-thread), but it takes time to build. If one decide to JIT compile it, it sort of becomes a scripting language and runs much slower.

Meanwhile, if some fellow competitive programmers want to do some app development, both front-end or back-end (e.g. cross-platform apps in Flutter or write servers), I strongly recommend learning Dart. If you are fluent in Java or C++, Dart will be a piece of cake for you (I was able to pick it up in less than twenty minutes). I really love its language design and it's my go-to language.