Congratualations on never actually bothering to block JS and find out - you know, facts. From actually doing so over many years, and so from actual experience I'd say completely non-functinal sites are about 25%.
I’d put the number quite a bit lower than that, probably comfortably under 10% of sites I interact with, though the trend is definitely upwards, drastically so among interactive things (which are probably worse than 50% broken these days).