As a consumer facing developer it was a slap in the face honestly.
Microsoft needs to remember that there are two types of developers, ones that build enterprise focused apps, and ones that build consumer focused apps. Seems like Nadella and minions have completely thrown in the towel on consumer. Every single presentation was geared primarily towards the enterprise space. All of this does not bode well for the MS Store, UWP, nor for the release of a Core OS based mobile device, since all of these are heavily consumer focused.
What did Build 2018 say to companies like Fitbit, Hulu, Netflix, Spotify, Facebook, Pandora, Slack, WhatsApp, and others who have stuck with the store for a number of years now? I guess we'll see. But my guess is that more and more big name brands will leave the store. Why shouldn't they? Microsoft has all but officially abandoned the consumer space. One by one they will wake up to that reality and abandon the Microsoft ecosystem as well.
If you are a consumer focused developer my advice would be to start learning Android Studio and Java as soon as possible. The writing is clearly on the wall.