Whew. Quite some time has passed, quite some things have occurred.
But CDPs live on! As I've moved on from independent analyst / consulting life, there's not much sense in holding back the old CDP Buyers' Guide, which has been viewed by thousands of individuals at hundreds of companies around the world, and continues to drive new registrations on this site. So folks still need help... and this site will remain, so that I can continue to post and invite others to share as well.
You can download the guide, which is clearly dated (came out November 2018), but might still offer some insight, here: CDP Resource's 2018 Q4 Customer Data Platform Buyers' Guide
I would still welcome any feedback on this self-published (thanks Canva!) guide, positive or negative, though if you are a provider I would welcome you to write a publishable explanation of where you are today, and how you would categorize your technology, so that it can be shared here.
Where I've headed since the guide, which would have definitely been included if ever there were a revision, is that a customer data platform must be a thing that the entire organization understands. The software components that make up the organizational customer data platform not so much -- but what the customer data platform does for the business, how it protects customer data, how it makes customer data useful... these things should be understood across the organization, which will make building out an actual customer data stack a lot easier as getting buy-in is baked into the organization. Define your customer data platform, then buy one (or two or three).