The lack of boundaries below national level is off-putting. Both the style and the tile spec itself seem to need a lot of refinement... highways look like a patchwork at low zoom. I had also thought shortbread excluded a lot of POI types, but maybe I need to review again.

But that's not to diminish the accomplishment overall here for the OSM page itself– this is an awesome step forward!

OSM has always overdone boundaries in my opinion, the raster tiles show national/international waters and electoral districts, which are of limited use for most purposes.