This is a small critique, but I wish there was some foreshadowing of High Guard's existence.
In the movie their appearance is kinda abrupt, and I don't remember them being mentioned anywhere beforehand. We only find out who they are and what their deal is after Bumblebee and Starscream infodump a little bit. And then that's kinda it.
Like, I initially thought that there will be a small timeskip where D-16 is separated from the rest of the group and by the time they find him he already has a small army of followers who also want to kill Sentinel for one reason or the other.