As much as I love this film myself (it's even my favourite animated film of all time), user ratings are entirely subjective. Just because we all think it's amazing doesn't mean everyone else will agree with us. Some people might simply regard it as merely a good film but nothing special, or even just decent or merely okay. And that's fine; they're allowed to feel that way.
Also, as Gentle Sharptooth was saying, 7.4 is still a pretty good score. It's well into the positive range. An okay rating to me would be in the high 5 range, or possibly low 6. LBT is still rated higher than many other animated films from around that era, or just a lot of animated films in general. Or even non-animated films; there's plenty of other movies with ratings in the mid-6 range or even lower that I really enjoy. But that doesn't mean that their ratings are automatically wrong; it just means I don't feel the same way myself.