The truth is that there are just way too many characters for there to be sufficient characterisation and for there to be enough the films would have to be even longer. To add to this these are action films which demands well placed action sequences to keep the audience engaged. Remember how people complained about the pacing in TF1? The Transformers are the action sequences in a human heavy series. Will people be satisfied with long gaps between action is instead of human characterisation we had TF characterisation instead? The best way to get this characterisation is either to create longer movies or more movies. People say that Prime did characterisation right however they conveniently omit the fact that there are more episodes and the characterisation has primarily been done through episodes specific to a single character. This would be impossible in the films as we can't have 23 minutes dedicated to one character when there is such a large cast. We could have had a few minutes of characterisation but it still wouldn't add up to much unless they added them in every now and then, building up across not only TF1 movie but throughout the entire series so far.