All resorts are going to require some walking and some additional modes of transportation. No
DVC resort is going to put you within walking distance to more than two parks. So, the question is really which resorts are best at efficiently transporting you to your destination of choice.
My vote would be for the original DVC studios at Poly or, as others have said, Riviera.
The Poly studios are nice simply because of where, within the resort, they are located. It's an easy walk to anything transportation related, including the TTC. It's the only resort where you can get directly on the EPCOT monorail with an easy walk. Granted, the walk anywhere there is going to be mostly uncovered (and you might prefer a similar-distance walk down a long, climate controlled hallway in, say, the rain or heat). The tough sell on Poly is that it does share a bus with the Grand Floridian at times (Poly is the first stop). Given that these are two busy resorts, and given the road construction that is currently going on within and right outside Poly, it's a significant drawback, and one I'm always hoping they'll reconsider, especially when the dust starts to settle on the new tower. We've never had a problem with the MK monorail at Poly -- its monorail stop always seems to be less crowded than the other two monorail resorts for some reason.
Rivera is nice because I believe it is the only DVC resort that does not have internal bus stops and does not share a bus with another resort/building at the resort. In other words, once the bus to or from the only stop at Riviera's lobby starts moving, you know no one else is getting on or off it until you reach your destination. Add in the Skyliner for EPCOT and HS, and its centralized location if you are doing a rideshare, and it checks all the transportation boxes nicely. The transportation-related drawback to Riviera is that, while it gets "good grades" for all destinations, it does not get "great grades" for any one in particular, whereas you have other resorts that allow you to easily walk to one or two parks or Disney Springs. As much as people dread the idea of a walk at the end of the day, it's so nice to not have to wait on anything to come pick you up and to be able to avoid the bus/skyliner/boat lines at park open/close.