Comment by AdmiralAsshat

I actually think Calibre's kitchen-sink approach is great. By-and-large I don't really need the fifty things it does to be best-in-class. If it's good enough, then it's fewer UNIX-style utilities I need to download on top of my existing installation.

For example, for end-to-end ebook creation or editing, I would probably download Sigil. But for the majority of e-book edits that I do (generating or fixing a broken Table of Contents, correcting the odd typo here and there, looking at the CSS rules that are causing the book to display weirdly on my Kobo, etc), Calibre's e-book editor is fine.