a single font can contain a maximum of about 65000 glyphs, but there are over 150000 defined Unicode glyphs, so a single font of last resort isn’t possible, unfortunately. Complete coverage would require multiple fonts.
The poster for Colossus:Forbin was very disappointing. The title sequence graphics for the movie were great - but the poster doesn’t show a computer at all, although the movie is all about them.
I suspect that few professional (paid for) adverts use any fonts from dafont.com, and many fonts would anyway be unavailable to ordinary users. The current font recogniser programs are usually trained on commercially available fonts
There is some research which suggests that the human brain “learns” to read an unfamiliar font reasonably fluently after about 30 minutes of use, and that recognition continues to improve with continued use. The well-known saying “we read best what we read most” suggests that a font itself contributes only partly towards readability - your personal habits and experience are also significant.