They call that out as an improvement with the rust switch. You can now just scp a single binary over and have fish without even needing to install it

Same. That's why I stick with zsh, even though I know Fish has better features, and I would really like to learn fish. I log into many different VMs every day, they all use Bash, some also have zsh. None of them have Fish.

I only have to "quotes" strings that contains globs. The rest mostly work or use the newer/recommanded way to do things for posix shells.

But I must admit, I only use it interactively. For scripts I #!/bin/{,ba}sh. I will use something else once it won some/most the distro preinstalls (either nu, elvish, fish, but for now it's sadly python).