For smol things like left-pad, sure but the two examples given (moment and react) solve really hard problems. If I were reviewing a PR where someone tried to re-implement time zone handling in JS, that’s not making it through review.

In JS, the DOM and time zones are some of the most messed up foundations you’re building on top of ime. (The DOM is amazing for documents but not designed for web apps.)

I think we really need to be careful about adding dependencies that we’re maintaining ourselves, especially when you factor in employee churn and existing options. Unless it’s the differentiator for the business you’re building, my advice to engineers is to strongly consider other options and have a case for why they don’t fit.

AI can play into the engineering blind spot of building it ourselves because it’s fun. But engineering as a discipline requires restraint.

Whether that's true about React and Moment varies on a case-by-case basis.

If you're building something simple like a contact form React may not be the right choice. If you're building something like Trello that calculation is different.

Likewise, I wouldn't want Moment for https://tools.simonwillison.net/california-clock-change but I might want it for something that needs its more advanced features.