"There's no structure to your writing"
Issues could be caused by:
Only you know where to place your emphasis.
"You have outlined the main theories well, but the question asked you to 'compare and contrast'. This means you need to expand on the similarities and differences, and the implications and importance of these."
You need to make sure you understand what is being asked of you.
Check that you understand what all the words in your assignment title mean.
"Your assignment describes the different ideas and theories, but does not examine why the key points and main features of the theories are significant."
"Assess and analyse the evidence from your reading and then bring together your own views in response to your reading in a conclusion at the end of the assignment."
Analysis and evaluation involve discussing the ideas of different writers in depth and questioning their validity.
You may also receive feedback that your writing is too descriptive. This means that you have simply outlined an idea without identifying how it is significant.
"You have made some good points, but haven't supported your arguments with sufficient evidence."
Make sure that you support your points by referring to relevant literature, and include full details in your reference list.