The Lord of the Rings

Regarding the film, it's characterized by stark minimalism. Anduin is portrayed as a great river, but the Melekezka (for those unfamiliar, it's a tributary of the Kama, which in turn is a tributary of the Volga) is actually wider! And what kind of country is Gondor if Minas Tirith offers a view of almost the entire Osgiliath, even though it's located approximately half an hour away?

This isn't really that important. The main point is that the film accurately reflects the essence of the book – and that's what matters. Although, of course, there are some parts that didn't make it into the film – for example, it's a shame that there wasn't room for the episode about Tom Bombadil...
But compare it, for example, to Lukyanenko's "Night Watch" – now there's a case of the opposite problem.
"Excessive detail" ruins the reputation of the original story, in my opinion. It's no wonder that all the films in the saga have won numerous Oscars! (I - 7, II - 4, III - 11(!), if I'm not mistaken), and you're talking about "minimalism."

Both the film and the book seem rather boring to me. That is, it's the typical Tolkien style. I don't understand why he constantly burdens the narrative with uninteresting, unnecessary, and tedious details?

I can't understand how someone who has read the books and is also a fantasy fan can say that! The books are read in one breath – one part of the trilogy in one night, or even one and a half! You probably haven't read any truly boring books – just ask, and I'll recommend some for comparison