I mean, I use all kits all of the time. Most of the time I choose healer or tank depending on the game mode. Sometimes I use builder or chef depends on the map. I only use chef when I knew someone is rushing me and use builder when I'm either rushing or fighting back a rusher.
The very least kit I often use is chef obviously cuz it doesn't really help that much unless you're rushing or something.
imo, all kits are useful if you're using it correctly.