Unsure if you were trying to make a point to debate the article; but it appears they're specifically speaking of private networks, not public.
Given how saturated the spectrum is, its remarkable how reliable wifi has become. I get occasional dropouts (maybe once or twice a day for a few seconds) but otherwise my connection is rock solid. And this is all over 802.11ac - which is super old at this point.
Most consumers never upgrade their router, and even if it fails, telcos often send them old and outdated replacements. There's a lot of networks around that are still stuck on older technologies.