I think I am too used to the core utils to move away from them. I'm not fond of colors and interactive filters anyway, so I'm fine with keeping them. Their behavior is also more predictable because defined by POSIX.

I do think however that some tools should be part of the core utilities, and thus "extend" my core utils rather than replace them:

sponge (moreutils)
Reads ALL input before writing to output. Useful for "inplace" operations.

pick (mptre)
Simple interactive selector for the terminal. I know that I said I'm not fond of "interactive" commands, but they are sometimes handy, and I'd rather have a dedicated tool for that, rather than have it built into every single tool, each with a different interface.
I use it mostly to select hostnames out of the nearly 2000 hosts we have at work.
This is a much simpler version of my work script (I retrieve host list using an API with curl(1)):
abduco (brain-dump)
Session manager, replicating the "detach" feature of tmux. This is the replacement for the now outdated "dtach" (which still works great).