I agree although your 0.01% figure is way off. Official marketshare is still 1.5%. Also… those of us who have been doing plugins for a long time (I started when 10.3 came out…) have long-term customers with a higher chance of using old software.
Still I agree JUCE should drop 10.6.8. support, but ideally not in between master branch version releases.
I don’t build on Linux, but I think requireing libc++ might have some consequences for that as well?