Is it truly unspeakable horrors or is it lazy writing that just lets the mind of the reader do the imagining of unspeakable horrors for you?

Yeah that's what I thought too. The horrors are described well, they just typically don't get described through their physical form. As you say, because the human mind cannot comprehend it. There is a lot more focus on impressions, comparisons, and effects, rather than on a real physical description. Personally I thought it was quite neat!

Yes and also, people's reaction to the horror of often what gives it its punch. Like how the shark in jaws or even the alien in Alien are both good designs, but the actual reason they're so scary is because of how all the characters around them react to them.

The idea of Italians befouling the hamlets of New England with their swarthy presence and animalistic hand gestures gave him conniptions.

I've been listening to Lovecraft audiobooks and at no point he mentions Jewish people in any of his work. His racism and hate was very blatant towards black people, native American and foreigners, especially of Asian origins. In one of his stories, he explicitly attack kurds, black and Chinese people all at once.

I genuinely want to know where people got the info that he hated jews. I mean, it's not like it's something Lovecraft wouldn't do, but what perplex me is his hate for Jewish people is often the only thing people mention, while his hate for black and Asian people was so much more explicit in his work.