I agree with many points raised here.

Provide CLI tooling and you can build integrations with any editor! A while back Microsoft published Language Server Protocol [0]. I'm sure there must've been previous attempts achieve this, but I'm not aware of any that were widely successful. Meanwhile LSP seems to be gradually growing [1]. Having a common interface seems like such a sensible idea too! With that said, I think the software community has largely standardized on Unix. Is it unreasonable to expect OSs to implement a Unix-compatibility layer? Given that Windows is working towards that goal, is there any other major holdout?

Code formatters make tons of sense. It lets you shift the responsibility over to the computer. I think it should also be possible to have an editor visually format code in your own preferred style, while saving the output in the project's preferred style; although I haven't seen this implemented by any editor yet. In the web community, Prettier [2] has been growing increasingly popular. It currently supports JS, CSS, and GraphQL in many of their flavors (e.g. JSX, Flow, TypeScript, etc.); and there's ongoing discussion about supporting others like Markdown [3], and probably others which I haven't seen.

Dependency management is one of the big pain-points of dealing with older languages. I want to be able to pull in APIs that correctly solve my problem without sacrificing cross-platform support. Sometimes I want to load multiple versions of a library. Setting up a working build environment shouldn't require multiple hours or days of work. As an example, I've wasted multiple days over the last few months trying to build android for either my Pixel or Nexus 5X, using Ubuntu, and I haven't been successful. I can't count the number of times I've lost interest in projects because I couldn't get it to build after spending countless hours, sometimes days, trying to setup a working environment. I have my fair share of criticisms of the web development community, but at least it's never a problem getting one of their projects to build.

Testing is important! I think this is something that Swift is doing well. They have a list of projects [4] which they automatically test against the development branch in order to understand the compatibility impact of their changes. With their latest set of breaking changes they also provided tools to help gradually migrate to the latest version [5]. I'll note I haven't worked on a serious production-ready Swift environment, so I don't know how effectively these tools work for a serious real-world projects.

Version control is a must, but I'd also suggest trying out more tools, rather than limiting yourself to git. I've used git professionally, and I can work with it without breaking anything. But plenty of its commands are needlessly confusing and quirky, and it's too easy to shoot yourself in the foot. Relevant XKCD [5]. I've had cases where I shot myself in the foot and Time Machine's file history was the only thing that saved me. Fossil [6] is a really nifty alternative, written by the creator of SQLite. It's much friendlier, and it includes an issue tracker and wiki! I've been happily using it for some of my personal projects. It's not the right tool for every problem, but it never hurts to try out something new.

[0] https://github.com/Microsoft/language-server-protocol

[1] http://langserver.org

[2] https://prettier.io

[3] https://github.com/prettier/prettier/issues/2444

[4] https://swift.org/source-compatibility/

[5] https://xkcd.com/1597/

[6] http://fossil-scm.org