And I'd reckon a large proportion of the "not on EDSM" stars within 5000 LYs of Sol will have been "discovered" by those people who try exploration and don't like it, or simply those who are slugging out their 5000 LY torture for Palin.
The "not on EDSM" stars within 5,000 ly-s? I've found unvisited systems 600 ly from Sol. Also, I've recently scooped up all the non-EDSM systems in a real nebula's sector, that has an asteroid base, also well within "Palin range". About a third of those were entirely unvisited (and no mass code A systems were present), and this is about as low-hanging fruit as it gets.
From what I hear, many of the people who don't like traveling for the Palin requirement just blow their ship up once they've made the distance. After all, if 5,000 ly was torture, why would they do 10,000 ly instead?
The majority of non explorers will not be flying outside the known bubble and extended routes.
If by the extended routes, you mean Sol - Colonia - Sagittarius A* - Beagle Point, then it's not just the non-explorers: the majority of explorers are around these lines. Beyond that, the most popular form seems to be to travel from popular destination A to B (usually nebulae) and explore the systems the route plotter gives along the way. Take a look at EDAstro's decaying heat map, EDSM's traffic report videos and their Commanders Map: there are quite few Commanders who set out into the deep galaxy
Also, note that EDSM also gets data from other tools that non-explorers use. Technically, it's the EDDN, Elite Dangerous Data Network. Take a look at the statistics: 42.3% of Commanders there are Aimless. (And 16.5% are Elite, making it the second most-common exploration rank, or the most common non-zero one.)
Or hey, I just realised that EDDN has a status page
here. The software distribution is also quite interesting there.