There are some reasonably stable packages in the npm ecosystem, it's just pretty much the Wild West out there. It really depends on what you're building. It's pretty hard to get a new SPA started these days without a development environment which uses npm, especially if you're running lean.

The problem is keeping your dependency tree reasonable. Even pulling in a couple of packages might lead to hundreds of dependencies. And even if you have the sense not to use an external package for something as simple as left-padding a string, someone somewhere in that dependency tree might not feel the same way. And that's all it takes to bring a chunk of the web down.

All of these problems of course are due to JS not having a mature ecosystem or standard library. People shouldn't need to reinvent the wheel every hour, nor should they be pulling in modules less than a dozen or two lines of code. That, and the constant misguided financial incentive to deploy ever more complex functionality over http are what lead to this aggressive push for cutting edge tools.