The movie was indeed quite juvenile, more-so than the first, but I didn't have a problem with his height. There's plenty for me to complain about but height isn't really one of them.
We all know Carnage is traditionally leaner than Venom, usually with comparable height. However both have had variable and inconsistent height in the comics in years past. Sometimes Venom gets
a lot beefier, sometimes Carnage gets
a lot taller. It's really up to the story/artist. In some recent comics Carnage has
become quite a bit taller than Venom.
So ultimately, I would say while it is not *typical* for Carnage to be so tall, it is not that outlandish either. The height is more open to interpretation, I don't take issue with it. Movie Carnage's overall
build still appears stringier/leaner than Venom's smooth bulk, so they got the most important aspect of his build right. His personality on the other hand...