
At work our "front end" code is a mish mash of Vue and React with builds driven by Gulp, Grunt and Webpack. We're trying to move to TypeScript and standardise on React, but it leaves us with the same problem of "legacy" code that I'm sure afflicts most web projects. I'm responsible for the back end code (Java and C++), but working closely with the front end team has given me some insight into their pain.
It would be so good if the major web browsers could start supporting TypeScript natively, and remove some of JavaScript's more stupid features (the messed up equality stuff being chief amongst them). Given that TypeScript is a superset of standardised JavaScript, all the optimisation work on the JS engines would not be lost.
And as the survey respondents note, a standard library would be a massive improvement. One thing that has helped keep our Java code relatively compact is the class library. It lowers the bar for new people working on the code, since we're not using myriad different libraries to do similar things. It also improves security and stability, since the standard library is generally well designed, consistent and updated along with the rest of the core Java platform.
As for build systems, in the Java world we also suffer from duplication - Ant (although that's very legacy now), Maven and Gradle. I loathe Gradle, thanks to it being based on Groovy and being essentially a scripting language masquerading as a build system, but that doesn't mean I love Maven. However, having one half decent build tool is at least an improvement over the JS world. We even have projects that use a combination of JavaScript build tools to overcome deficiencies in each other!