My guess is that you are asking in the wrong forum. The people who visit here will likely be "power users" who use wide range of calibre's functions. For example, I seldom use the three functions you mention, but very frequently use others.
My most-used functions are sorting, the search box, saved searches, restrictions, and the tag browser. Next down the list are edit metadata (both dialog and directly on the GUI), quick view, and connect to device/folder. Next down are send to device/folder, delete from device/folder. Next is edit metadata bulk. And so on.
When I add a new book (an infrequent event), a different set of functions come into play: add, edit metadata, manage authors, manage tags, manage my custom metadata, etc. The goal is to ensure that the metadata for the book is quality, and that the existing books' metadata is still quality in the face of the new book.
I almost never download metadata, I very seldom use the viewer or cover browser or save-to-disk, and I don't use the built-in content server.