The other 4 movies did really at the box office because that was back before Transformers' significant foothold in popularity. Once 2007 film came about and brought along positive buzz, people were willing to give the sequels a chance. However, the designs were still a popular complaint. Read any of the comments on social media—many of them revolve around how they can't understand the fight scenes due to how muted in color the Cons were. And now since Transformers has become an icon in popular culture today, many people are now expecting for the designs to have some resemblance to their source material. In the era of Marvel movies and nerd culture, the expectations are much different than they were back then. I was personally a fine with the Bayverse designs. I still collect the toys and I'm happy having them on my selves, but it's getting stale seeing a sea of nameslaps and it's time for something new. Plus, it's much more exciting to see characters that actually look like the characters they're supposed to be.