If the foot is not accelerating, then that means it has a net force of $0$ acting on it. Since the static friction force acts forward, this means that there is another force acting on the foot that has a component pointing backwards. The only place this force can come from is the leg, and this makes sense. By Newton's third law, if the leg is pushing backwards on the foot$^*$, then the foot is pushing forwards on the leg, which is what we want to have happen if we are trying to walk forward.
Of course this is a huge over simplification of walking, which involves multiple steps (pun always intended) and many interconnected body parts, forces, etc. But I think just the simplistic view I present above is useful in the initial understanding of why the net horizontal force acting on the foot is $0$ for the part of the step where the foot is on the ground.
$^*$Of course vertical components of these forces are important as well, but of course the vertical components of the forces acting on the foot cancel as well (at least in the part of the step where the foot is not accelerating vertically). I don't think analysis of these vertical components is important for this discussion focusing on horizontal movement due to friction though.
If some how there is a force that act on feet somehow the static friction just balance it,it can't be greater than that force. 1:For bodies not in relative motion (static friction), $$0 \leq f\leq \mu N$$.