The ship designs are very different in the prequels, yes. But they are that way for a reason and just because they aren' the same designs we grew up with doesn't mean they are inferior.
The Republic is a peaceful, developed society that values diversity, culture, art and all the other things we associate with a good society. The Emire is the exact opposite. Every Imperial is an old white human male. There are no aliens, no racial minotiries, and no women in the Empire. There ships have an industrial look to them. They value function over form and are completely devoid of color.
Lots of color is used in the prequels while almost none is used in the Imperial warships. The Republic was this great developed society that was paved over by an uncaring and self-serving machine.