Now I see that questions closed as duplicate are hidden. They are visible only to the post author and users with the close/reopen votes privilege.

That means that these questions will not be shown in search engines.

Before the recent change dupes were shown to everyone and they were very useful to point to canonical answers. That increased chances for people who search to find a correct answer. Now we lose all that.

Also some dues have good answers that are hidden now too and lost to the public.

This looks very sad to me.