Official? I've never heard this as official doctrine. Can you point me to anything official?

I'd love to see OpenStreetMap.org be more directly useful to more people, rather than only as a "developer site".

"developer" is a slightly weird way of putting it. osm.org is the contributor portal and demo site for OpenStreetMap, and yes it is not and never has been intended as an end user replacement for Google Maps and similar offerings.

The main purpose of the maps on the site is, besides showcasing some topical uses of OSM data, rapid feedback to contributors, which is something that required specific development so that can be provided with vector tiles too.

The 'late to the game' narrative seems to be a bit misplaced in any case given that OSM data has powered essentially all vector tile use outside of Google over more than a decade.

Well that's a bit of a balancing act, isn't it? "Why isn't this feature on the site, it would be more useful to me; also, that feature is annoying and useless to me" - says literally everyone.

Thus, we get a built-in editor (less friction, yay/too rudimentary, boo) and popups (OSM events, yay/Popups are now everywhere, boo). And endless discussions on "this should be more/less prominent."

I don't think there's any official edict, but the approach "I don't like this and I'll make my own version" is at the very least workable (as opposed to, say, Google Maps).