SELECT COUNT(*) FROM SYS.ALL_VIEWS;
Is not a simple query. ALL_VIEWS is a very complicated view, it has many joins requiring special logic to determine what the calling user is actually allowed to see.
You can use all_views to see the logic behind all_views, this is how it looks on 19c.
select OWNER, VIEW_NAME, TEXT_LENGTH, TEXT, TEXT_VC,TYPE_TEXT_LENGTH, ...