The only real advance in call center tech in the last twenty years (imo) has been the “press 1 to be called back in the order your call was received”.
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.