Roller shutters do not darken - really no reason for complaint?

Hello dear forum,

we have the problem that our roller shutters do not completely darken the room.
We have a small child who can only sleep in total darkness. And a lot of light comes through the roller shutters. When the little mouse wakes up, she of course sees everything and does not go back to sleep. On the one hand, the light comes through the side of the individual slats and on the other hand, the rail is so short that light also comes through the lower corners. I am attaching a picture.
Our construction manager and the roller shutter company say that a roller shutter does not darken completely and they see no reason for improvement. But now we are facing the problem and it concerns our little mouse who cannot sleep. And I wonder why the roller shutters in my 30-year-old parents' house darken properly and also those in rental apartments, which are often built cheaply, do as well.
What do you think about this?
Is this really standard?
And is there maybe another solution so that the roller shutters darken better?

Please take a photo without flash. You can only guess at it this way.

We had curtains in our apartment that darkened the room accordingly... And I am also sensitive to light in the bedroom.

Many thanks for your reply.

The picture is without flash.

Are those really roller shutters or rather venetian blinds?

It looks like the rail profile does not extend to the windowsill.

Yes, they are really roller shutters.

And yes, the rail does not go all the way down. We addressed this and were told it can't be done differently because otherwise one would not have been able to get in with the exterior window sills.