Here's my thoughts on my primary issues with communication:
A couple years ago (2011?), Mike Mearls announced they had lost touch with the fanbase and were establishing new weekly columns for the website to improve communication. Now we know this was to gather marketing feedback for the direction of D&D prior to the public playtest.
When the new edition was released, the articles stopped. Which gives the impression that, once we had given the information needed to make the new edition, our feedback wasn't really needed. Once they had made the hit game, communication was no longer needed.
There are still the surveys every so often, but that's different. It's more feedback to design rather than feedback prior to design and guiding design. There's even a need for it: Mearls has sometimes put out calls for feedback on twitter. That's great for rapid responses, but you're not going to reach everyone, just the twitter users who follow D&D designers and checked their feed in a one-hour window.
It's not a great way to talk to the fans, as it requires the fans to reach out to you, not the other way round. The social media sites are okay, but they're mostly used as a marketing tool announcing things and sharing articles rather than communicating or interacting with the fans. There's no dialogue and limited seeking of information.
For example, an article on psionics would have been a good idea. Musing about the design and getting feedback prior to the Unearthed Arcana article. That might have sidestepped some of the "Far Realms" and "mystic" controversy. They could also look into which subclasses are more desired, which subsystems people like, and what optional rules feel missing from the game.
There's also a wealth of monsters that didn't make it into the 5e Monster Manual that could be considered for feedback, or extended feedback. How do the fans feel about primordials? Death giants? How should yugoloths/daemons be handled?
At the same time, the designers have been absent from podcasts and fan interviews. I don't remember the last time Mearls of Crawford was interviewed. They tend to limit themselves to the official podcast, that is also mostly a marketing tool.
It's a very one-sided form of discussion. Advertising and marketing on the social media, rules questions on twitter, and feedback for things they already designed on their website. There's very little actual communication going on, and what little there is, is restricted in scope and topic.
Which is odd because the team is so very approachable. I've seen them at GenCon and they're great guys, and friendly. It feels like there's this wall between us and them unless you're right there in person.