I think a lot of people who watch and enjoy Transformers films and aren't/weren't fans of the toys don't actually care too much about the characters outside of the most important ones like Optimus. It's not like a comics universe where it's quite possible for even a non-comics fan to be aware of and permanently remember the smaller characters like Falcon, Pepper Potts, Shuri, Wasp etc. And it would be criminal to forget anyone who's had a solo or the likes of Widow or Vision. But I bet those same audience members would struggle to name more than a handful of Transformers or even remember them aside from the ones who look particularly distinct. I think even outside of execution skill, some concepts are much more/less well fitted to being a cinematic universe and easier/more difficult to develop that way.