The best part about fish is you don't have to configure it much to be productive in it. It is really nice that the fish maintainers think hard about what should be configurable, and what sane defaults should be. This is not as common as it should be in OSS. Contrast with zsh, which has a billion knobs to tweak, and the consensus is that everyone should install a huge "community dotfile framework" (whatever that means) consisting of tons of opaque aliases and settings, some of which might make your shell startup lag.
More to a specific point: I haven't had much of an issue with fish's subshell/backgrounding control. That doesn't mean that there aren't issues, just that my interactive use doesn't trip into them.
I will note that you can write an async git prompt using nothing but fish itself, which I consider an advanced use case for a shell. Check it out: