(...) but most people prefer to read in their native language.
I'm not so sure about that. There are a lot of foreigners living here and many (foreigners and, mostly young, Germans) speak English good enough they could/ do read English books. E.g., we went to the Joker movie last thursday and the room was full; Netflix/ Amazon prime sometimes launch movies only with German subtitles and add synchronisation later (or never because there is none), our biggest book store in town center has several shelves of English books in the entrance area.
Within my bubble of fantasy authors, a lot of them say they tend to read English books because they can't find what they like in German books. (Translations are common but, how it is, the one book you're looking for is not.

Like good books about writing.) They are also usually people who read books with diverse characters (POC, gay, etc.).
So I wouldn't say it's an absolute waste. The potential is there, question's just how big it is (and within which genres).