Aside from the drone, it's a Curiosity rover with upgraded tires (and diff instrument package). I think that is actually an incredibly exciting statement, not boring: Nasa has such high confidence in the refinement of Mars rovers that they're only making small changes now.
From what the guide at JPL said when I went on a tour there and got to see the Perseverance rover in the cleanroom, was that they simply had enough spare parts from building the Curiosity that it was easy/worth building this second one.