Calculate electrical box volume needed
All grounds count 1. (per @ThreePhaseEel's comment, more than 4 are now 1/4 count each as of NEC2020)
One yoke device (the outlet) is 2
6 wires terminating in the box are 6
If there are cable clamps in the box, those count as 1. If they are outside the box, they don't count.
14Ga so 2 cubic inches per count.
So: 18 or 20 cubic inches. Pigtails (wires that don't leave the box) are free. Wires count the same if they terminate on a wire nut or terminate on a device.  Your box isn't big enough, you are correct about that. A box can be legit and still be hard to pack in (the free things are not really free that way) but the box you have is not legit as wired.
Side note. Using the backstabs is highly dubious and frowned upon by anyone who has removed a half-melted device using them, or actually had a fire started by them. How they ever got approval is beyond me. Use the side screw clamps or devices that have a screw clamp on a different type of back wire entry.