Everything has to go VOIP, though I think it isn't a utility. Can you call email a utility?
VOIP is very very poorly done across networks. There is very poor standard compliance or just no standards & proprietary lock ins. Throw in ISPs NATing (& no IPV6) and you get a world of pain and stagnation, which we are in.
I currently happily pay for a decent VOIP service through AAISP. I think there is plenty of innovation in voice calls like having a (short) number for life (esp useful when abroad), higher quality calls & proper logging. "The" VOIP iPhone client is 3CX which sucks. WebRTC doesn't seem to have a VOIP client that works. Another important limitation to note, is that you can't run a VOIP client on a mobile to receive calls on Android or Iphone since it kills the battery.
I don't see how a nationalised network helps. Unless that network got rid of NAT and did IPV6 and fostered interoperability.
Otherwise the existing network is fine, it's just that Telcos must allow for better VOIP (SIP2SIM) bridges. If this is an indication of the current state of UK SIP2SIM stuff here http://revk.www.me.uk/2013/12/sip2sim-relaunch.html then it's pretty bad if you ask me.