I've previously used Perl rename[1], but as it has no safeguards, I find rnr much more pleasant to use.
[1]: https://manpages.ubuntu.com/manpages/xenial/man1/rename.ul.1...
However, for me this operation is so rare that having a separate command just for mass-renaming files does not seem to be justified.
[1]: https://github.com/thameera/vimv