You can do it from your profile settings: Username -> Settings -> Blocks. Just type names/partial names then click to add. Don't prefer Hentai? Type "hentai" and you can click all the various communiies. It works best when having the full community list page open in a seperate tab to be able to see the various names.
That being said, I do think the Community list page is a hot mess that the Lemmy project needs to improve. As you mentioned, it would be nice to block there. It also would be nice to sort on that page.