Ok, so if I visit a site with malicious JS it can now potentially steal the contents of my ram at a blistering few KB/s for the duration that I am on the site.

Ok, so if I visit a site with malicious JS it can now potentially steal the contents of my ram at a blistering few KB/s for the duration that I am on the site. That's really not that big a deal compared to slowing everything down again. Modern computers are slow enough thanks to the mountains of abstraction developers insist on using (web included!), the realtime AV scanner, Ads, user tracking, and just general software bloat.