Are LNs really the irredeemable garbage they appear, or is it the fault of the translators?
Six of one, half dozen of the other. Japanese literature doesn't really translate well to the familiar styles of western writing, so at times things don't flow as well and the translation is harder. The Haruhi LN translations I read are all perfectly acceptable insofar as language, but the temper and flow of discussions, scene changes, description, and so forth, is either lacking or different in approach.
However, there is also just a lot of garbage LNs. With the boom of the industry in the last ten years, you are going mathematically get a lot more chaff with your wheat.
Most LN are harems trying to ride that wave so yeah, most are irredeemable garbage with little originality. Authors see what made others famous and try and piggyback on it. That's why you get so many MMO LNs or incest themed LNs.
A lot of the time it reads like an highschool essay in japanese too, especially when they are using weird kanji in their chuuni LN and you don't know if he's doing it ironically or if he really wrote 尽滅 to sound cool
16 years ago I was just wondering what the fuck a light novel was.
There would be no loss if light novels just died overnight.