Now this is an excellent question. I think inherently, they're a good idea. Having extra healing spots throughout the game is a good thing, especially on long routes and dungeons where the nearest Pokemon Center is light years away. Best of all, you have to earn them by beating them in a battle, which adds a sort of challenge to them. However, I think it is the frequency of healing spots in 5th gen that is problematic, not the Doctors and Nurses themselves. For instance, on Rt. 7, you can heal in one of the houses there, and yet there's healing spots in Mistralton City and Celestial Tower. The Pokemon Center in Mistralton and the Nurse in Celestial Tower are useful because of their location, but the one on Rt. 7 is not. It gets pretty absurd in some cases, the most extreme example I can think of is Rt. 4 in BW2. You have the Pokemon Centers in Castelia and Nimbasa, you have a rest house near the entrance to Desert Resort, and you have Nurses within Desert Resort proper and in Join Avenue after you reach Rank 4. All within the span of two relatively close cities. Do we really need that many? So no, Doctors and Nurses are fine, we just need to keep them in spots where it's too far or takes too long to go back to the nearest Pokemon Center.