Here's a quick short list of things that developers still have to write because the current implementations are broken, buggy, inconsistent or absent:
- Date pickers.
- Image upload [1].
- Autocomplete and datalist.
- Range pickers.
- Upload time remaining without javascript.
- Number min/max/step, use up/down keys to increment/decrement.
- Form elements that are unable be styled by CSS.
- Color picker (arguably not as important as the others, and some OS color pickers suck anyway).
[1] Basic things like resize image on the browser prior to uploading. Size, aspect ratio, crop could be hinted by the html or chosen by the user. Server check is still needed, but upload size and times would be reduced drastically.
Shouldn't those be more important?
Original www is very successful at mouse-based UX, but horrible at touch based.
Actually browsers could agree on a dozen touch based standard input elements and we don't need 80% this JS framework cruft.