Seems a bit drastic. Don't use it as the main font in a japanese textbook, sure, but use it with the disclaimer that it's not perfect and will get some readings wrong? Why not, still pretty useful. Should people also not use Google Translate? (also, you can stuff an entire llm in a font, it's been done).
If I asked you 'are you a sewer (pronounced "soo-er")?', would that make sense? Maybe if you looked at it hard enough and thought about it, but in the meantime, I would probably get some very strange looks for asking.
Yomitan only shows readings for words you explicitly hover over and press a modifier key, so it doesn't distract you, and when you do explicitly ask for a word, Yomitan will show all the readings and definitions.
I'd agree that 80% is better than nothing if you have no alternatives, but you do. I don't know about Furiganator, but Google Translate is also much better than 80%.
Stumbling on names is fine, name litteraly have no logic, there is no system that will get them 100% correct by definition.
Screwing meaning is on a whole different level and Google Translate or even the built in screen reader of your OS will do an extremely good job given enough context (a whole phrase).
In real world use there is little space for sloppy hacks IMHO.
Google translate does not - I see it get readings wrong on very basic sentences with plenty of context on a daily basis. It doesn't make it useless. The website mentioned the font wouldn't show furigana if the reading was ambiguous so I was basing my judgement on that, obviously if it's just always wrong, that's not useful.