A GPS approach without WAAS is actually more accurate than an ILS, at least horizontally. A GPS fix without WAAS is, IIRC, accurate to 10 meters. and you get that all the way from the IAF to the MAP. WAAS doesn't help a lot with horizontal accuracy, it was implemented to get vertical accuracy good enough for use with precision approaches, giving a glideslope.
Like it or not, the current navaid system is going to go away, because it's simply not economically viable. The maintenance costs on aging analog systems, using vacuum tubes in many cases, are just too high to be kept up. We're no longer flying range approaches, and I predict we won't be flying NDB or VOR approaches that much longer. Technology advances, and we have to give up obsolescent parts of it.