I'd argue that the correct solution then is to have better support to style native components if designers are going to do it anyway.

Additionally, it is not terribly difficult to make a custom checkbox , for instance, accessible. It may require JS and ugly DOM, but I wouldn't say it's difficult.

Date and time pickers are harder. All the platforms have a native control, and all major browsers except Safari on MacOS expose it.

That one omission means the control is basically unusable without some sort of polyfill, at which point you might as well just use the same JS implementation everywhere because why not. :/

The the drop down on select not being customizable is also famously irritating.

Nearly all browsers have a native date/time control, true. Also true - many browsers do it quite badly. So eventually I always end up using the JS solution...

e.g. There's no way (by design!) to override in CSS the browsers' date format detection - and the method differs by browser/OS combination. Some customers can't manage to configure it, so end up with the american format when they want the european format. Also more than a few native browser date controls are very underfeatured (e.g. current Edge).

Date time is a nightmare.

I am thankful for momentjs literally every day I do web development. I know it gets a lot of flack for it's bundle size, but it makes so many things easy.

Heck the native JS Date object can't even give an ISO time string in the same time zone the date object was created in. Not to mention a dozen other deficiencies.

Dealing with time had always and probably will always be painful.

And then there is China, where they use YYYY-MM-DD, but 12 hr time with an AM/PM equivalent. So close to doing it the correct way!

Ugh.