As stated above the Impreza is an entry level vehicle for Subaru. It wasn't meant to have features that would make you consider it over the Legacy other than better fuel economy. Honestly, the interior aside from being smaller (IMO) is nearly as nice as the interior of a Legacy with fabric from the same time period. That would be the 2000-2004 Legacy model, I think the same goes for Imprezas and Legacy models since this time. Although the GD Impreza may have come two years later, it was designed to fall into a slightly aging family of vehicles as the Forester and Legacy based vehicles were at mid life or older by this time.
I guess if you have a dealer optioned Impreza with leather or an STi Limited, the interior gets even nicer and again closes the gap between it and the Legacy interior other than size. The Impreza interior was also better than vehicles it competed with from the same time period. Your Impreza may be a 2007, but you have to realize the design dates back to 2002 and is now almost 12 years old. My 2003 Sentra SE-R Spec V had an interior that looked nice but everything was made of cheap hard plastics, although manufacturers using premium plastics will say its not cheap...premium just means it doesn't look as cheap as other plastic dashes and has nicer textures.
Many brands switched to the premium plastic dashes including Subaru, but they are recently going back to soft touch dashes like the ones in our cars I believe...a lot of these new interiors look nice on newer cars but I feel like you're getting less because of the materials they are made out of...again they only look nice and up to date now that dash designs are more complex/artistic and visually engaging.
If you want to do something...upgrading to 2004+ WRX seats might make things a little better for you but honestly I think you'd be best off saving your money. It isn't going to make it a new car and the only way you will greatly benefit from the seats is if you are regularly doing some spirited driving as they are slightly more snug than the standard Impreza seats, other than that they just look different and that to me isn't enough to truly go out and spend a few hundred bucks and that's if you're lucky enough to find a set worth buying for that price. Anyway GL.