Oh Koa! It all depends on how the language is handled. There's nothing wrong with German as such. For example, from a purely linguistic point of view, Kafka writes extremely simply and clearly.
I'm a bit surprised that more hasn't been said about Guenther Grass. He's quite popular, at least in translation.
It's widely acknowledged that since the 1980s there has been a very sharp fall in the numbers learning German in the English-speaking lands and this may have had an effect on interest in German literature, too - even in translation. On the whole interest is in 20th century literature.
Incidentally, one of my favourites is Heinrich Mann, "Der Untertan". I think part of it has been translated (as "A Man of Straw" ?) but as far as I know it hasn't been translated in its entirety. Obviously, it's satirical and some background knowledge is useful.
As for the absurd in Kafka's work, surely that's only to be expected as it's one of his central themes.
