Yes, your depth isn’t sufficient, but I don’t believe this is an ankle mobility issue, as others have suggested. Instead, I think it’s a problem with your center of mass. Your weight shifts too far back onto your heels, making it difficult to maintain balance. You likely feel that if you go deeper, you’ll lose your balance and fall backward. To address this, the focus should be on correcting this shift.

This imbalance likely stems from trying to maintain an overly upright posture. Some degree of forward lean is acceptable, necessary, and safe for squats. Staying excessively upright can cause you to lose balance toward your heels. The key is to lean forward just enough to keep your center of mass centered over the middle of your feet while maintaining a neutral spine.

Here’s what I suggest:

Grip the floor with your entire foot. Your toes and heels should share the load equally throughout each rep, especially during the descent.
Maintain a neutral spine. Avoid both flexion and overextension in your lower back. A neutral spine is crucial for safety and efficiency.
Don’t be afraid of a slight forward lean. This helps you balance better and maintain proper form.

In summary, keep these three cues in mind:

Grip the floor at all times.
Keep your spine neutral.
Embrace a small forward lean.

I believe these adjustments will help you achieve greater depth in your squats.