The only real advance for the customer (if you don't count voiceprint authentication, natural language IVR, agents having all your customer details ready as the call connects saving lots of tedious dictation).

On the business side, you have real-time load metrics to feed your automatic workforce management, rerouting of calls based on staffing and load, highly accurate transcription and sentiment analysis that's always on (even when you think you're on hold, always mute your phone), the accessibility of enterprise-grade contact centres to SMB, and about a dozen other things that weren't possible 20 years ago.

My dentist has a PBX setup so that when you call and you don't get anyone or leave a voicemail, you get a link in a SMS with a link to schedule a call back.