No resort is close to everything, and there is no pixie dust in transportation.
The Crescent Lake resorts have fantastic access to Epcot and good access to Studios. To all other destinations one needs to deal with Buena Vista Drive. That's gotten better now that they've widened it in some spots, but it is still a traffic light gauntlet. I haven't been at RIV long enough to experience its connectivity to the rest of the World beyond the Skyliner destinations. I suspect it is a little better than Crescent Lake, but only just. I happen to like the Skyliner, but I also don't visit during the rainy season, so YMMV.
The Monorail resorts are extremely convenient to MK. Wilderness Lodge is also very good. Poly is convenient to Epcot (the longhouses more than the tower). Any other trip from the MK area requires you to pack your patience, because it is going to take a while---and this is the same reason every other resort is not particularly convenient to MK. The new flyovers have helped a lot in both directions.
OKW is conveniently loacted to a main artery, but the internal bus route is a pain with all the dead-end turnarounds---staying somewhere where you can get off at Pensinsular and on at Carriage House helps a lot. SSR is only slightly less convenient to an artery, but its internal circulation route is much less frustrating, so I've found it to be better overall. The easy access to Disney Springs is a big plus, IMO. AKV is much closer in time than in space to most other destinations, because there is only one traffic light (at Sherberth) between it and any other theme park, and the rest of the trips are all on aterial roads.
I do usually rent a car. It is my second "splurge" after hoppers, and I generally drive most places not named Magic Kigndom or Disney Springs---for both of those, the parking lot is either far (MK) or painful to get in/out of (Springs). I will sometimes skip the car if I am staying in Crescent Lake or RIV, because the only route that driving helps with is AK. I will also usually drive one afternoon to MK to take the ferry over and back if the weather is nice, unless I'm at the Lodge where boat access is an everyday thing.