Yep, it can take a while. The 60-90 minute estimates are sort of "worst case scenarios." Say you arrive at the bus stop and a bus has just pulled away. It might be 20 minutes before another one arrives. (And it could be more if things aren't running smoothly.) Once it arrives, it still has to unload...if there are scooters, this could take a few minutes. And loading can sometimes take a while, too, for the same reasons. Once you're on the bus, the stops depend on where you're going. If you're at a park and going to a resort, that resort could share services with other resorts and you might stop at those first. Factor in waiting for unloading and loading at each stop. For instance, if you're at Animal Kingdom and going to the Grand Floridian, that bus will usually stop at the Contemporary and Polynesian first.
If you're going from resort to resort, you are going to have to transfer somewhere in almost every case, so take the above and double it. (Again, worst case.)
In general, the WDW property is not walkable. In a few areas there are sidewalks along roadways, but not many. Some resorts are positioned so that they are walkable to parks (you can walk from the Contemporary to Magic Kingdom and from the Boardwalk, Beach/Yacht and Swan/Dolphin to Epcot and Studios), but that's it. Some resorts are connected by walkways - you can walk from Grand Floridian to the Polynesian, Animal Kingdom Lodge's Jambo House and Kidani Village, or between the three All-Star resorts. You can also walk from the All-Star Resorts to Blizzard Beach and McDonald's. There is a walkway from Saratoga Springs to Downtown Disney...two, actually, but one is closing for DTD construction.