Your feet tell you a lot about what’s happening above them, at rest and during movement.
The posture (position) your feet are in is the result of what’s happening upstream. Your foot position is intimately related to how well you control the position of your pelvis and how well your hips are able to function as a result of this.
The stability, strength, and control of your hips and pelvic musculature determines whether you can maintain control of every joint beneath them, and therefore maintain the desired position of your joints at rest and during movement.
It comes down to having control over your joints, and attaining/maintaining the desired joint positions as you move.
Your feet can grant your body a huge amount of stability IF they are in a good position. If you can use your hips and pelvic control to get your feet where you want them, then they have a huge amount of intrinsic muscles that can work to your advantage. But the feet need to be in a desirable position (posture) in order to work optimally.
All of this can be worked on and changed. The body changes and adapts to what you expose it to. Learning to control your body requires attention and focus at the start, but is essential for overall musculoskeletal/joint health.