I use it alongside starship because it came preconfigured on my distro (this also means all I may say might not be caused by fish itself, sorry)

Things I love the most are :

• the extended history integration. You can type part of a command you typed in the past, and using up/down arrows will let you navigate through all commands matching
• the extended autocompletion. Typing the start of a command you already ran before will let you press right arrow to use that whole command again (you can use shift or control, idrr, with the arrow to complete word per word) Typing something in your terminal (say, mp4) when no commands start with mp4 will list all known commands that have the symbols m, p and 4 in order (they can be separated by any symbol)
• I find it easier to program than in bash. Beware, the syntax is slightly different than with bash

I may have forgotten stuff but that's a good start IMO