I think death of Optimus and growth of hotrod by itself is fine if it was intended to be the last chapter of the g1 transformers story (the execution was poor, but death of a father figure and young guy growing up to fill the role is just another hero's journey) and if transformers were just a traditional ip (like comic book super heroes) that happened to have occasional toys and merchs instead of an ip built up intended to be toy commercials. I imagine the anger from fans wasn't necessarily because they killed off Optimus, but the cynical reason behind such action