I get the impression he's not just talking about coloring, but also about what labels to show, how to space and lay them out, etc. He mentions this explicitly:
> [...] the real challenge for a map service is to decide what they should and should not display. Google does an excellent job [...]
It doesn't follow that because CartoCSS/Mapbox studios is "editable", "customizable", and "easy", that the specific combinations of configuration and adjustment available would meet his complex criterion of minimizing time, effort, money, and aesthetics. I'd imagine Google Maps is optimized to a T for all of the tiny specific label placements you want, and I'm not convinced from the one-off choice it would have been a 100% better idea for the OP to use.
It might have been a better choice, and maybe he didn't evaluate the option, but I still imagine the complexity of these options for the OP's specific aesthetic taste is quite large.
There is indeed no great solution to 'prominence' in the OSM data. There have been efforts to add population information to places, and to promote so called villages into so called towns when they are locally important, but those efforts have not been completely systematic (so they might be better in Austria than Minnesota, and even worse in Wisconsin).
Which is one reason to turn to the Natural Earth data, it has been curated more systematically than OSM.
> There is indeed no great solution to 'prominence' in the OSM data.
There has been lots of research about how to automatically produce Goldilocks Maps (enough information - but not too much) - I remember an article (whose URL I can't locate) which showed increased readability by pruning minor location names when they are too close to major locations. Google does that sort of thing well, but they are not the only ones nowadays - for example the osmfr Openstreetmap style does, in my opinion, a decent job of prioritizing labels: http://tile.openstreetmap.fr/
I looked around the local area here and it turns out to be quite reasonable, but there are also more than a couple misses, where the more notable town/village in a pair is suppressed.
Or for the interested, TileMill would be better as you can print exports in PDF as vectors. I spent a great deal of time trying to manually create transit maps for one of our 'archaic' transit agencies, and this was before Mapbox Studio's time. I use Studio a bit, but TileMill does the better job as it caters better for offline usage.
I do agree with others though that it would have been a great amount of effort to invest in understanding CartoCSS for his requirements, and getting to create it.
Google does do a very good job at this for online maps - but as you can see in his photographs, it is absolutely the wrong choice for a wall. Having the ability to change the labelling of a map to suit your needs is cartography and the OpenStreetMap map making toolkit is one of the better ways of achieving this.
> [...] the real challenge for a map service is to decide what they should and should not display. Google does an excellent job [...]