That's for another time though. For now, I'll just cut to the chase and copypasta something I wrote a couple years ago regarding translation quality between professional and amateur work:[1]
Japanese has a very rich history and is also significantly more expressive than English is, so academic teaching of the language can only do so much. You really need to immerse yourself in Japanese literature/media and partake in just ordinary day-to-day conversations to simply begin to understand the depth of it all.
Translation is also hardly an appealing job unless you find love in the art of translating itself, speaking as someone who has done translating as a hobby (both FGO and otherwise). Almost nobody knows or cares about the effort that goes into translations, most readers only care if it "sounds right" in English. Keep in mind that the vast majority of people who read the bad translation pointed out in the OP won't realize it's bad. It's very hard to keep yourself motivated when your readers don't and can't give a crap about your work.
So combine a language that is very different from English with people who probably aren't all that motivated anyway, and most professional translations end up being shit. The work is thankless and giving more than the absolute minimum quite sincerely doesn't pay off because the readers don't know and can't care.
Good translations require passion from the translators and the editors, passion that simply just isn't there outside of the hobbyists and enthusiasts who enjoy the art of translating rather than doing it for their paychecks.
[1]: https://old.reddit.com/r/grandorder/comments/dnpzrh/everyone...