For experimentation and prototyping I tend to check out new things, those might end up in the 'boring' stack once I'm familiar with them.
For me it's a personal stack of tools that work for me, and I try not to be too influenced by what's the next new thing on sites like StackOverflow or Hackernews, I use what works for me and what makes my clients happy.
99% of the developers here aren't even close to needing to think in terms of that scale, beyond simply not doing dumb things in your code that can happen no matter what tools you use. Hell, there are whole companies that don't need to do these things. A few companies I've worked for or contracted with were bogged down, IMO, because someone couldn't settle for "adequate", making the company suffer because their architecture is so hard to figure out.
I like using "boring" tech(in particular Ember.js, Node.js, Ruby, CouchDB and PostgresSQL/SQLite) because if something gets the job done in a reasonable amount of time, most of which I think comes down to having a competency with a set of tools, then I really don't care very much for drinking from the firehose of frameworks and libraries.
Letting go of ego is tough but, when you do, you're freed from the need to be "like Twitter" or "like Uber" and instead just build things using tools you are genuinely interested in or work for you. It's one thing if you really have the desire to be the kind of wizard to work at Google(and not be relegated to writing shell scripts all day), but if that isn't for you that's fine because the vast majority of jobs out there don't need an archmage.
What most companies need is someone who is going to KISS and not eff things up. If you can do that, you'll have a hard time getting fired even if you sometimes slack off.
There really is no reason to use plain JS for anything!
unless you don't want to compile your code. I can spin up little projects that don't need a build step just fine.
I have a relatively neutral opinion of Typescript, but oh boy does that quote ring true. TS can be a very nice safety net when refactoring (just fix all the type errors, and the app should mostly work as it did before), but you can also very well paint yourself in a corner with similar-but-slightly-different types all over the place that'd just work if it was in JS.
Sometimes newer technologies get hyped, but interestingly the most popular ones like React and Rust are also quite boring in many senses (React introduced a new model of programming web views, but stuck to plain JavaScript concepts, didn't try to reinvent the wheel for every component (e.g. like Angular having it'a own special http library) and has been incredibly reliable with few breaking changes from day 1. Rust introduced the idea of a borrow checker, but otherwise intentional borrows most of it'a ideas from other langauges and doesn't try to invent new ways of doing things, and again is incredobly stable and reliable from an implementation point of view)
In seriousness, the phrase "boring technology" is, to me, a reference to the talk "Choose Boring Technology" [0], which has been discussed on HN numerous times [1] (deservedly, because it's great).
The author doesn't explicitly say what boring technology is, but uses examples you'd generally expect: postgres, php, python, memcached, mysql, apache web server.
Basically, products that have been doing relatively complicated things (interpreted code, rdbms, key-value stores) for a very long time.
Explicitly, he says that "boring technology" is technology that's defined by its very low maintenance cost. He claims that maintenance costs are mostly driven by uncertainties around failure conditions and design. These kinds of uncertainties are especially present in newer stacks, where the opportunities for footguns and unspecified failure conditions abound, because people are still working them out.
He implicitly references Redis as a fancy new technology, but a lot of people today would probably consider Redis "boring" (unless you're trying to use it as your RDBMS).
[0]: http://boringtechnology.club/
[1]: recently, here: https://news.ycombinator.com/item?id=20323246