why everytime I watch a jojos part the first 4 eps are very good, the middle is so boring and the last 4 eps are the best eps ever seen

Im watching part 5 right now and it feels like every part is like this, am I the only one who thinks this?

An example is how part 3 was 48 episodes, lots of the fights just felt unnecessary to the plot

it's like almost every part is just a bunch of enemies coming one by one until the main characters actually fight the actual antagonist