There are places where improvements on both dev experience and user experience intersect. For example, if the big browsers all delivered a much more robust set

There are places where improvements on both dev experience and user experience intersect. For example, if the big browsers all delivered a much more robust set of easily styleable standard widgets, that would benefit devs by reducing the amount of custom widget work needed and benefit users with more consistent behavior and reduced payload sizes. Things like that should be prioritized the most. Once all of that is taken care of, browser vendors could start doing cycles of switching between focus on dev experience and user experience.