> I would love to hear of other low(er) barrier-to-entry ways to use LaTeX, because it’s a pretty steep commitment for someone who isn’t a professional writer.

I have been working on and off on a fork of LaTeX with real-time feedback: you can see the document and error messages rendered and updated live. It also supports SyncTeX (going from a source line to the corresponding output and vice-versa).

I added vim support recently, you can see it in action there: https://github.com/let-def/texpresso.vim There is also emacs support in the main repo (https://github.com/let-def/texpresso). That's all quite experimental, but I hope to do a first release next year. It should work on most unix, I test with Linux and macOS.