I mostly agree with the stated opinions here, extending coreutils is fine, but replacing is a no-no.

One other reason I’m hesitant to jump onto all those “like X but nicer (and in Rust)” tools is that by getting used to these, I forget how to use coreutils. I’m frequently SSHing into production boxes at work, where there are only coreutils, so knowing how to use them effectively is somewhat important when things are on fire.

That being said, I only use fd and ripgrep from the new school of tools. I wouldn’t know how to do ripgrep in coreutils (find + grep I guess), and fd really just to avoid typing out that annoyingly long find syntax every time.