Have you used the "new Style" OSM maps? Mine look like this and, since I use Mapsource I can easily adjust the level of detail easily. As a Mac user you are stuck with Basecamp, hopefully someone will come along and explain how you can adjust the level of detail in Basecamp
'Stuck', is an emotive word, given that BaseCamp works very well on a Mac. Leedude seems to work it very well on a Windows based PC, too. But hey...
I am away on a 19 night 'Lap of Germany' all the routes created / borrowed / stolen using BaseCamp and Garmin's own NavTec maps, on a Mac, without too much difficulty. The routes are all running on my bog standard BMW Navigator V (basic preference settings only, to avoid U-turns and unpaved roads) without a glitch. If I (with no IT degree and as someone does not understand one end off a root directory from another) can manage, any twit can.
From memory, when looking at the screen of a Mac running BaseCamp, there are two slider bars, down near the bottom of the screen.
1. The larger bar, zooms the map in and out
2. The smaller bar beneath increases / reduces the fine detail shown
You can also use the magnifying glass tool, to zoom into just a very specific area within a map.
Off course this presupposes that the owner of the Mac has the detailed maps installed / available / unlocked in the first place or they'll be zooming into the square root of feck all. It happens.
That's the basics done, without using the 'Find' function.
PS OSM (and other third party map providers) maps download, install and display easily on a Mac, running BaseCamp. Just as easily as they do in Mapsource on a PC. They also transfer just as easily from a Mac to a Garmin device as they do from a PC.