One small glimmer of hope is that customizable selects are indeed being worked on: see https://open-ui.org/components/customizable-select.explainer... and the broader work of the Open UI group at W3C.

I'd love to see this level of customization come to date and datetime-local popups, finding a meaningful path that preserves compatibility with the design languages of various platforms. If and when that happens, it will be because of the work of standardization working groups like Open UI and Interop.