calibre-web is not a replacement for calibre. The real hard part is all the ebook conversion stuff, which calibre-web can do by... calling calibre binaries. So saying "it has nothing to do with him" is quite the statement.

Calibre has saved my bacon countless of times. It's absolutely crazy how many crappily formatted epubs are out there (not pirated ones, mind you, but bought from stores). Without Calibre to clean these up, my reading experience would have been so much worse.