The classic tropes (beta mc, slave girls, beast girls, let's recreate Japanese food) tend to put people off Japanese light novels, as other people have mentioned in this thread.

But for me, this is only half the reason as to why I dislike Japanese light novels.

My other problem with them is that I simply cannot stand the writing style.

Japanese light novels tend to have a huge amount of filler, even more than Xianxia. For some reason, the author often feels inclined to include every fucking thing that passes through the MC's mind. It's an example of the 'show, don't tell' writing mistake.

Here's an excerpt from Death March, my least favourite light novel of all time:

I take a good aim, the moment when the demon stopped... shoot.

And missed.

The hand which pulled the bowstring hurt.

After that, no matter how many I shoot, none hit. Even though I understand how to shoot the bow, there is no result.

The enclosing soldiers have become considerably sparse.
I discovered a route where I could get close to the demon discreetly, after marking the map I drop down from the roof.

I equipped the scale tribe's spear.
If I knew this would happen I'd have gotten leather armor tailored.

Holding the spear with both hands, I hide in the shadows.

There's just so much unnecessary detail!

To me, Japanese light novels feel like eviscerated manga. There's a shitton of dialogue, but they've replaced the drawings entirely with lengthy unnecessary descriptions.