There are a ton of moving parts, if you will, in this discussion. First, I agree with those that state it is not a millennial issue. Also, to be mindful in casting a "broad net".
Personally, I have advocated that CS and inside sales should be paid a professional-level, entry-to-mid level salary based on experience. The challenge is first company culture, then economics...that is, it may not be feasible for a larger organization due to call volume.
Technology: Most in the under 50 demographic will use online services, chat, etc., for support and further direction. These folks are FAST in response. If it is not your preferred medium of communication, that is OK, but it is subject to the architecture of most current business practices.
Personally, I enjoy talking to a 'real person', but fact is I am also doing so online and it is mostly very expedient.
Last quick note and thought is: Professionalism. I am talking of behalf of the Company AND the customer...I understand if someone is on hold for long durations or having difficulty communicating that emotions can get the better of us...BUT, take a time out, relax/breath, in a 100 years will it really matter? I forgot who said it, but food-for-thought: in your vision of the world, is the reflection of yourself.
Poor service is inexcusable; not necessarily the fault of the person you are dealing with, however.