Building a dungeon is flatout old fashion. Most people start with an interesting location and maybe a couple of areas at each location. This is also how the starter sets are; they give you some easy locations to start off with. Why? Once you've learned how to run a location, you now know how to run a series of "rooms," as each location is made of sub-locations. From that point, creating a dungeon is basically just creating a connected series of "rooms."
Technical dungeon aspects, like traps, secret passageways, etc are intuitive ideas pretty easy to grasp. Likewise, visual aspects like jaquaying a dungeon aren't necessary to for a good starter dungeon. But even then, building a full, OSR-style dungeon is just not something a lot of homebrew DMs do. I'm drawing this data not just from social media and WotC, but also from my own anecdotes. I'm in a pretty large group of players -- over 30 people. We divide up into different games that go for different lengths (few weeks, few months) and rearrange based on who wants to do what at the time. We also have a lot of players ranging from lower 20s to 50s. What I've learned here is that, dungeons just don't appear a lot. Not traditional dungeons, I mean. There's just so much more fantasy to explore then dungeons IMO.
Now, the game is called Dungeons & Dragons. But IMO the real truth is, anything can be a dungeon so long as it has rooms and connectors, and any monster can fit in for the "dragon" role. So despite the name, classical dungeon building is just not that popular anymore. Nor is it necessary to play D&D.