Just to sum up what has already been pointed out in the comments: Methanol can have infinite conformations in free space due to free rotation of the C-H and C-OH sigma bonds. Hence, for any particular spatial conformation you can think of for the molecule, it can always develop a perfect mirror image for the same almost instantly(in case you are wondering about some time lag between them) as conformers are in chemical equilibrium.

So what this essentially means is that, suppose a some conformation A of methanol has polarized light in some direction (assuming the right-handed coordinate system, let's say the positive X direction) in some fashion(let's say circularly polarized, clockwise). Then, this particular interference pattern of light will be internally compensated by a conformation B of the molecule which will circularly polarize the light in the anticlockwise direction in the negative X direction. So, the emergent light ray will appear to be unpolarized for the observer

Just to sum up what has already been pointed out in the comments: Methanol can have infinite conformations in free space due to free rotation of the C-H and C-OH sigma bonds. Hence, for any particular spatial conformation you can think of for the molecule, it can always develop a perfect mirror image for the same almost instantly(in case you are wondering about some time lag between them) as conformers are in chemical equilibrium.

So what this essentially means is that, suppose some conformation A of methanol has polarized light in some direction (assuming the right-handed coordinate system, let's say the positive X direction) in some fashion(let's say circularly polarized, clockwise). Then, this particular interference pattern of light will be internally compensated by a conformation B of the molecule which will circularly polarize the light in the anticlockwise direction in the negative X direction. So, the emergent light ray will appear to be unpolarized for the observer