There doesn't seem to be any opportunities for pretend play
The materials don't seem to allow children to be creative
Children don't seem to be interacting with another very much
(1) When Dr. Montessori opened the first Children's House it was full of pretend play things. The children never played with them as long as they were allowed to do real things – i.e. cooking instead of pretending to cook. It is still true.
(2) The materials teach specific things and then the creativity is incredible. Like learning how to handle a good violin and then playing music. It is not considered "creative" to use a violin as a hammer, or a bridge while playing with blocks. We consider it "creative" to learn how to use the violin properly and then create music. The same goes for the materials in a Montessori classroom.
(3) There is as much interaction as the children desire, but the tasks are so satisfying that, for these few hours a day, children want to master the challenges offered by them. Then they become happier and kinder—true socialization. Also, since concentration is protected above all, as all "work" is respected, children learn early on not to interrupt someone who is concentrating.