I wouldn't call all of Lovecraft's style terrible. A lot of it is just dry.
But his dialog IS terrible, which is why his stories rarely include it. I get the impression of a man who didn't talk a lot with other people face-to-face. He was much more into correspondence and that comes out in his writing, and why so many of his stories take the form of correspondence.
So ideas: A+.
Execution: C+, on average. Some stories are better than others, likely due to brevity.
Kadath is weird but doesn't really feel like a proper Lovecraft story until it gets to the part where he notices some of the mountains seem to be moving.
I forget where but I remember reading something that said
The Doom That Came To Sarnath and
The Dream Quest of Unknown Kadath were both homages to a similar kind of story, set in a fantastical city, written by a contemporary of Lovecraft's.
Kadath is one of his earlier works too so it's likely he was cribbing another author's style closely, which is why it doesn't fit nicely with his other stories.
editAh. Right. Lord Dunsay. Guy used to write a lot of poetry and I think that's why
Kadath seems weird for Lovecraft. I remember there's a lot of poetic prose in that, which isn't how you'd describe Lovecraft's later prose at all. It's pretty much the opposite of poetic and flowing.
I think one of my more favorite Lovecraft stories is
The Silver Key, because it's sort of about the dream cycle but excludes the mythos and most of the horror elements of his other stories.
Also Steven King stories would all around be better if he would drop the romance sideplots/main plots. Going back to the Dark Tower though, it's just his thing, which I guess you get out of a lot of late 70s, 80s writers: a preoccupation with sex. I really enjoyed the Dark Tower up until the main character starts shacking up with different women and there's whole weird vaguely misogynistic vibe going through it. And then later books just double down on it.
I think that's why many of his books make for decent normie fare though. People can relate to it a lot easier than, say.....Clive Barker, because it's drawing on the experiences of average midwesterners and easterns in small towns.