The ship changed quite a lot as well.

We had much less money to spend producing television shows in the 1960s than we do today and the technology of building sets and doing special effects has gotten so much better since the original series.

Gene also felt that if space travel in the future is going to become routine, the ships that they live on will have to be more like a home. They have to accommodate people and, potentially, their families, so they are more like luxury hotels than the somewhat austere and spartan look of the original series Enterprise.