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