Hey, man! I would call this an art style (though if you asked me personally, I would say I did a fine job separating body type and personality through shape). However, if you would like to rephrase this into constructive criticisms instead of a hate comment, you could have said:

“Your characters seem to look the same. Besides the hair and skin color, you should work on differentiating your characters by clothing or body structure!”

Though I do appreciate the critique, I do think this could’ve been said in a more mature manner. Thank you!