explain me why "the lighthouse" is good?

Assuming you're seriousposting here, I really like it, one of my favorite movies in recent years. Also helps I'm a fan of Dafoe and his hog. That said, I see why not everyone can like it, especially because it's much more of a slow burn.

For starters the acting, both of them put on an amazing performance. I mean, that monologue followed by "alright have it your way, I like your cooking" is amazing.

I really loved some of the directional choices Eggman chose, like a nearly square aspect ratio, to give the feeling of claustrophobia alongside the characters. The constant slow roar of the horn throughout. A certain level of ambiguity to leave it up for interpretation in the story.

Lots of allusions and symbolism symbology throughout. A few of the allusions off the top of my head, Sisyphus, Prometheus, Proteus, The Raven, the Lighthouse being the concept of the Holy of Holies, among other references.

There's more too it and a lot to like but I also understand why people don't like it. There's a lot of little details to piece together that gives the story more cohesion and understanding.