Studio Ghibli films are nominated every so often. This could be due to their associations with Disney, or it could be because Ghibli movies translate well to a Western audience where things like Shinkai do not.

Dunkirk is Christopher Nolan. He's an excellent director and Dunkirk was by far the best movie of the year. The Shape of Water is Guillermo del Toro. Critics love him and he generally does good stuff.

Your Name was quite frankly a train wreck. The first half was boring and the second half made no sense the second you thought about it. It's a bad movie to try and sell anime to the Academy Awards on. A Silent Voice is equally as bad because it's too melodramatic and mostly appeals to teenagers.

There have no been any recent anime movies that are Oscar level in a while other than Ghibli movies. Satoshi Kon sadly made his movies before it was viable to have them eligible for the Academy Awards. Mamoru Oshii hasn't made as many movies recently. Giovanni's Island is the most recent non-nominated Oscar level anime movie, which was 2014